Reliable Japanese engines Toyota series A. "Reliable Japanese engines"

20.10.2019

Transmission

Reliable Japanese engines

04.04.2008

The most common and by far the most widely repaired of Japanese engines is the Toyota 4, 5, 7 A - FE series engine. Even a novice mechanic, diagnostician knows about the possible problems of engines of this series.

I will try to highlight (collect into a single whole) the problems of these engines. There are few of them, but they cause a lot of trouble to their owners.

Date from scanner:

On the scanner, you can see a short but capacious date, consisting of 16 parameters, by which you can really evaluate the operation of the main engine sensors.
Sensors:

Oxygen sensor - Lambda probe

Many owners turn to diagnostics due to increased fuel consumption. One of the reasons is a banal break in the heater in the oxygen sensor. The error is fixed by the control unit code number 21.

The heater can be checked with a conventional tester on the sensor contacts (R- 14 Ohm)

Fuel consumption increases due to the lack of correction during warm-up. You will not be able to restore the heater - only a replacement will help. The cost of a new sensor is high, and it makes no sense to install a used one (their operating time is large, so this is a lottery). In such a situation, less reliable universal NTK sensors can be installed as an alternative.

The term of their work is short, and the quality leaves much to be desired, so such a replacement is a temporary measure, and it should be done with caution.

When the sensor sensitivity decreases, fuel consumption increases (by 1-3 liters). The operability of the sensor is checked by an oscilloscope on the diagnostic connector block, or directly on the sensor chip (number of switching).

temperature sensor

If the sensor does not work correctly, the owner will have a lot of problems. If the measuring element of the sensor breaks, the control unit replaces the sensor readings and fixes its value by 80 degrees and fixes error 22. The engine, with such a malfunction, will operate normally, but only while the engine is warm. As soon as the engine cools down, it will be problematic to start it without doping, due to the short opening time of the injectors.

There are frequent cases when the resistance of the sensor changes randomly when the engine is running at H.X. - the revolutions will float.

This defect is easy to fix on the scanner, observing the temperature reading. On a warm engine, it should be stable and not randomly change values from 20 to 100 degrees.

With such a defect in the sensor, a “black exhaust” is possible, unstable operation on H.X. and, as a result, increased consumption, as well as the inability to start "hot". Only after 10 minutes of sludge. If there is no complete confidence in the correct operation of the sensor, its readings can be replaced by including a 1 kΩ variable resistor or a constant 300 ohm resistor in its circuit for further verification. By changing the readings of the sensor, the change in speed at different temperatures is easily controlled.

Throttle position sensor

A lot of cars go through the process of assembly and disassembly. These are the so-called "constructors". When removing the engine in the field and subsequent assembly, the sensors suffer, on which the engine is often leaned. When the TPS sensor breaks, the engine stops throttling normally. The engine bogs down when revving. The machine switches incorrectly. Error 41 is fixed by the control unit. When replacing a new sensor, it must be adjusted so that the control unit correctly sees the sign of X.X., with the gas pedal fully released (throttle closed). In the absence of a sign of idling, adequate regulation of H.X. will not be carried out. and there will be no forced idling mode during engine braking, which again will entail increased fuel consumption. On engines 4A, 7A, the sensor does not require adjustment, it is installed without the possibility of rotation.
THROTTLE POSITION……0%
IDLE SIGNAL……………….ON

MAP absolute pressure sensor

This sensor is the most reliable of all installed on Japanese cars. His resilience is simply amazing. But it also has a lot of problems, mainly due to improper assembly.

Either the receiving “nipple” is broken, and then any passage of air is sealed with glue, or the tightness of the supply tube is violated.

With such a gap, fuel consumption increases, the level of CO in the exhaust increases sharply up to 3%. It is very easy to observe the operation of the sensor on the scanner. The line INTAKE MANIFOLD shows the vacuum in the intake manifold, which is measured by the MAP sensor. When the wiring is broken, the ECU registers error 31. At the same time, the opening time of the injectors sharply increases to 3.5-5ms. and stop the engine.

Knock sensor

The sensor is installed to register detonation knocks (explosions) and indirectly serves as a "corrector" of the ignition timing. The recording element of the sensor is a piezoelectric plate. In the event of a sensor malfunction, or a break in the wiring, at over 3.5-4 tons of revs, the ECU fixes error 52. Sluggishness is observed during acceleration.

You can check the performance with an oscilloscope, or by measuring the resistance between the sensor output and the housing (if there is resistance, the sensor needs to be replaced).

crankshaft sensor

On 7A series engines, a crankshaft sensor is installed. A conventional inductive sensor is similar to the ABC sensor and is practically trouble-free in operation. But there are also confusions. With an interturn circuit inside the winding, the generation of pulses at a certain speed is disrupted. This manifests itself as a limitation of engine speed in the range of 3.5-4 tons of revolutions. A kind of cut-off, only at low speeds. It is quite difficult to detect an interturn circuit. The oscilloscope does not show a decrease in the amplitude of the pulses or a change in frequency (during acceleration), and it is rather difficult for a tester to notice changes in Ohm's shares. If you experience symptoms of speed limit at 3-4 thousand, simply replace the sensor with a known good one. In addition, a lot of trouble causes damage to the master ring, which is damaged by negligent mechanics while replacing the front crankshaft oil seal or timing belt. Having broken the teeth of the crown, and restored them by welding, they achieve only a visible absence of damage.

At the same time, the crankshaft position sensor ceases to adequately read information, the ignition timing begins to change randomly, which leads to loss of power, unstable engine operation and increased fuel consumption

Injectors (nozzles)

During many years of operation, the nozzles and needles of the injectors are covered with tar and gasoline dust. All this naturally interferes with the correct spray and reduces the performance of the nozzle. With severe pollution, a noticeable shaking of the engine is observed, fuel consumption increases. It is realistic to determine clogging by conducting a gas analysis; according to the readings of oxygen in the exhaust, one can judge the correctness of filling. A reading above one percent will indicate the need to flush the injectors (with the correct timing and normal fuel pressure).

Or by installing the injectors on the stand, and checking the performance in the tests. Nozzles are easily cleaned by Lavr, Vince, both on CIP machines and in ultrasound.

Idle valve, IACV

The valve is responsible for engine speed in all modes (warm-up, idling, load). During operation, the valve petal becomes dirty and the stem is wedged. Turnovers hang on warming up or on X.X. (due to the wedge). Tests for changes in speed in scanners during diagnostics for this motor are not provided. The performance of the valve can be assessed by changing the readings of the temperature sensor. Enter the engine in the "cold" mode. Or, having removed the winding from the valve, twist the valve magnet with your hands. Jamming and wedge will be felt immediately. If it is impossible to easily dismantle the valve winding (for example, on the GE series), you can check its operability by connecting to one of the control outputs and measuring the duty cycle of the pulses while simultaneously controlling the RPM. and changing the load on the engine. On a fully warmed-up engine, the duty cycle is approximately 40%, by changing the load (including electrical consumers), an adequate increase in speed in response to a change in duty cycle can be estimated. When the valve is mechanically jammed, a smooth increase in the duty cycle occurs, which does not entail a change in the speed of H.X.

You can restore work by cleaning soot and dirt with a carburetor cleaner with the winding removed.

Further adjustment of the valve is to set the speed X.X. On a fully warmed up engine, by rotating the winding on the mounting bolts, they achieve tabular revolutions for this type of car (according to the tag on the hood). Having previously installed the jumper E1-TE1 in the diagnostic block. On the “younger” 4A, 7A engines, the valve has been changed. Instead of the usual two windings, a microcircuit was installed in the body of the valve winding. We changed the valve power supply and the color of the winding plastic (black). It is already pointless to measure the resistance of the windings at the terminals.

The valve is supplied with power and a control signal of a rectangular shape with a variable duty cycle.

To make it impossible to remove the winding, non-standard fasteners were installed. But the wedge problem remained. Now, if you clean it with an ordinary cleaner, the grease is washed out of the bearings (the further result is predictable, the same wedge, but already because of the bearing). It is necessary to completely dismantle the valve from the throttle body and then carefully flush the stem with the petal.

Ignition system. Candles.

A very large percentage of cars come to the service with problems in the ignition system. When operating on low-quality gasoline, spark plugs are the first to suffer. They are covered with a red coating (ferrosis). There will be no high-quality sparking with such candles. The engine will work intermittently, with gaps, fuel consumption increases, the level of CO in the exhaust rises. Sandblasting is not able to clean such candles. Only chemistry (silit for a couple of hours) or replacement will help. Another problem is the increase in clearance (simple wear).

Drying of the rubber lugs of high-voltage wires, water that got in when washing the motor, which all provoke the formation of a conductive path on the rubber lugs.

Because of them, sparking will not be inside the cylinder, but outside it.
With smooth throttling, the engine runs stably, and with a sharp one, it “crushes”.

In this situation, it is necessary to replace both the candles and the wires at the same time. But sometimes (in the field), if replacement is impossible, you can solve the problem with an ordinary knife and a piece of emery stone (fine fraction). With a knife we cut off the conductive path in the wire, and with a stone we remove the strip from the ceramics of the candle.

It should be noted that it is impossible to remove the rubber band from the wire, this will lead to the complete inoperability of the cylinder.

Another problem is related to the incorrect procedure for replacing candles. The wires are pulled out of the wells with force, tearing off the metal tip of the rein.

With such a wire, misfires and floating revolutions are observed. When diagnosing the ignition system, you should always check the performance of the ignition coil on the high-voltage arrester. The simplest test is to look at the spark gap on the spark gap with the engine running.

The closed coil resistance can also be checked with a tester. The resistance of the secondary winding of the broken coil will be less than 12 kΩ.
The next generation coils do not suffer from such ailments (4A.7A), their failure is minimal. Proper cooling and wire thickness eliminated this problem.
Another problem is the current oil seal in the distributor. Oil, falling on the sensors, corrodes the insulation. And when exposed to high voltage, the slider is oxidized (covered with a green coating). The coal turns sour. All this leads to disruption of sparking.

In motion, chaotic shootings are observed (into the intake manifold, into the muffler) and crushing.

" Thin " malfunctions Toyota engine

On modern Toyota 4A, 7A engines, the Japanese have changed the firmware of the control unit (apparently for faster engine warm-up). The change is that the engine reaches idle speed only at 85 degrees. The design of the engine cooling system was also changed. Now a small cooling circle intensively passes through the head of the block (not through the pipe behind the engine, as it was before). Of course, the cooling of the head has become more efficient, and the engine as a whole has become more efficient. But in winter, with such cooling during movement, the temperature of the engine reaches a temperature of 75-80 degrees. And as a result, constant warm-up revolutions (1100-1300), increased fuel consumption and nervousness of the owners. You can deal with this problem either by insulating the engine more strongly, or by changing the resistance of the temperature sensor (by deceiving the computer).

Oil

Owners pour oil into the engine indiscriminately, without thinking about the consequences. Few people understand that different types of oils are not compatible and, when mixed, form an insoluble porridge (coke), which leads to the complete destruction of the engine.

All this plasticine cannot be washed off with chemistry, it is cleaned only mechanically. It should be understood that if it is not known what type of old oil, then flushing should be used before changing. And more advice to the owners. Pay attention to the color of the oil dipstick handle. He is yellow. If the color of the oil in your engine is darker than the color of the pen, it's time to change instead of waiting for the virtual mileage recommended by the engine oil manufacturer.

Air filter

When diagnosing, it can be erroneously assumed that the wear of the valve stem seals is to blame, but the root cause is a clogged air filter, which increases the vacuum in the intake manifold when contaminated. Of course, in this case, the caps will also have to be changed.

Some owners do not even notice that garage rodents live in the air filter housing. Which speaks of their complete disregard for the car.

Fuel filteralso deserves attention. If it is not replaced in time (15-20 thousand mileage), the pump starts to work with overload, the pressure drops, and as a result, it becomes necessary to replace the pump.

The plastic parts of the pump impeller and check valve wear out prematurely.

The pressure drops

It should be noted that the operation of the motor is possible at a pressure of up to 1.5 kg (with a standard 2.4-2.7 kg). At reduced pressure, there are constant shots into the intake manifold, the start is problematic (after). The draft is noticeably reduced. It is correct to check the pressure with a pressure gauge. (access to the filter is not difficult). In the field, you can use the "return filling test". If, when the engine is running, less than one liter flows out of the gasoline return hose in 30 seconds, it can be judged that the pressure is low. You can use an ammeter to indirectly determine the performance of the pump. If the current consumed by the pump is less than 4 amperes, then the pressure is squandered.

You can measure the current on the diagnostic block.

When using a modern tool, the process of replacing the filter takes no more than half an hour. Previously, this took a lot of time. Mechanics always hoped in case they were lucky and the bottom fitting did not rust. But often that is what happened.

I had to rack my brains for a long time with which gas wrench to hook the rolled-up nut of the lower fitting. And sometimes the process of replacing the filter turned into a “movie show” with the removal of the tube leading to the filter.

Today, no one is afraid to make this change.

Control block

Until 1998 release, control units did not have enough serious problems during operation.

The blocks had to be repaired only for the reason" hard polarity reversal" . It is important to note that all conclusions of the control unit are signed. It is easy to find on the board the necessary sensor output for testing, or wire ringing. The parts are reliable and stable in operation at low temperatures.
In conclusion, I would like to dwell a little on gas distribution. Many “hands on” owners perform the belt replacement procedure on their own (although this is not correct, they cannot properly tighten the crankshaft pulley). Mechanics make a quality replacement within two hours (maximum). If the belt breaks, the valves do not meet the piston and there is no fatal destruction of the engine. Everything is calculated to the smallest detail.

We tried to talk about the most common problems on Toyota A-series engines. The engine is very simple and reliable, and subject to very tough operation on “water-iron gasolines” and dusty roads of our great and mighty Motherland and the “maybe” mentality of the owners. Having endured all the bullying, to this day he continues to delight with his reliable and stable work, having won the status of the best Japanese engine.

I wish you all the earliest possible identification of problems and easy repair of the Toyota 4, 5, 7 A - FE engine!

Vladimir Bekrenev, Khabarovsk
Andrey Fedorov, Novosibirsk
© Legion-Avtodata

UNION OF AUTOMOBILE DIAGNOSTICS

Information on car maintenance and repair can be found in the book (books):

Engines 4A-F, 4A-FE, 5A-FE, 7A-FE and 4A-GE (AE92, AW11, AT170 and AT160) 4-cylinder, in-line, with four valves per cylinder (two intake, two exhaust ), with two overhead camshafts. 4A-GE engines are distinguished by the installation of five valves per cylinder (three intake two exhaust).

Engines 4A-F, 5A-F are carbureted. all other engines have an electronically controlled multiport fuel injection system.

4A-FE engines were made in three versions, which differed from each other mainly in the design of the intake and exhaust systems.

The 5A-FE engine is similar to the 4A-FE engine, but differs from it in the size of the cylinder-piston group. The 7A-FE engine has slight design differences from the 4A-FE. Engines will have cylinder numbering starting on the side opposite the power take-off. The crankshaft is full-support with 5 main bearings.

The bearing shells are made on the basis of an aluminum alloy and are installed in the bores of the engine crankcase and main bearing caps. Drillings made in the crankshaft are used to supply oil to the connecting rod bearings, connecting rod rods, pistons and other parts.

Cylinder firing order: 1-3-4-2.

The cylinder head, cast from an aluminum alloy, has transverse and located on opposite sides inlet and outlet pipes, arranged with tented combustion chambers.

The spark plugs are located in the center of the combustion chambers. The 4A-f engine uses a traditional intake manifold design with 4 separate pipes that are combined into one channel under the carburetor mounting flange. The intake manifold has liquid heating, which improves engine response, especially when it is warmed up. The intake manifold of 4A-FE, 5A-FE engines has 4 independent pipes of the same length, which, on the one hand, are connected by a common intake air chamber (resonator), and on the other, they are joined to the intake channels of the cylinder head.

The intake manifold of the 4A-GE engine has 8 of these pipes, each of which fits its own intake valve. The combination of the length of the intake pipes with the valve timing of the engine makes it possible to use the phenomenon of inertial boost to increase torque at low and medium engine speeds. The exhaust and intake valves are mated with springs that have an uneven winding pitch.

The exhaust camshaft of 4A-F, 4A-FE, 5A-FE, 7A-FE engines is driven from the crankshaft by a flat toothed belt, and the intake camshaft is driven from the exhaust camshaft by a gear train. In the 4A-GE engine, both shafts are driven by a flat toothed belt.

The camshafts have 5 bearings located between the valve lifters of each cylinder; one of these bearings is located at the front end of the cylinder head. Lubrication of the bearings and cams of the camshafts, as well as drive gears (for engines 4A-F, 4A-FE, 5A-FE), is carried out by the oil flow entering through the oil channel drilled in the center of the camshaft. Valve clearance adjustment is carried out using shims located between the cams and valve lifters (for twenty-valve 4A-GE engines, adjusting spacers are located between the tappet and valve stem).

The cylinder block is cast iron. it has 4 cylinders. The upper part of the cylinder block is covered by the cylinder head, and the lower part of the block forms the engine crankcase, in which the crankshaft is installed. The pistons are made of high temperature aluminum alloy. Recesses are made on the bottoms of the pistons to prevent the piston from meeting with the valves in the TMV.

The piston pins of the 4A-FE, 5A-FE, 4A-F, 5A-F and 7A-FE engines are "fixed" type: they are interference fit in the piston head of the connecting rod, but have a slip fit in the piston bosses. 4A-GE engine piston pins - "floating" type; they have a sliding fit in both the connecting rod piston head and the piston bosses. From axial displacement, such piston pins are fixed by retaining rings installed in the piston bosses.

The top compression ring is made of stainless steel (4A-F, 5A-F, 4A-FE, 5A-FE and 7A-FE engines) or steel (4A-GE engine) and the 2nd compression ring is made of cast iron. The oil scraper ring is made of an alloy of ordinary steel and stainless steel. The outer diameter of each ring is slightly larger than the diameter of the piston, and the elasticity of the rings allows them to tightly encircle the cylinder walls when the rings are installed in the piston grooves. Compression rings prevent the breakthrough of gases from the cylinder into the engine crankcase, and the oil scraper ring removes excess oil from the cylinder walls, preventing it from penetrating into the combustion chamber.

Maximum non-flatness:

4A-fe,5A-fe,4A-ge,7A-fe,4E-fe,5E-fe,2E…..0.05 mm
2C……………………………………………0.20 mm

Toyota power units of the A series were one of the best developments that allowed the company to get out of the crisis in the 90s of the last century. The largest in volume was the 7A motor.

Do not confuse 7A and 7K engine. These power units have no related relationship. ICE 7K was produced from 1983 to 1998 and had 8 valves. Historically, the "K" series began its existence in 1966, and the "A" series in the 70s. Unlike the 7K, the A-series engine developed as a separate line of development for 16 valve engines.

The 7 A engine was a continuation of the refinement of the 1600 cc 4A-FE engine and its modifications. The volume of the engine increased to 1800 cm3, the power and torque increased, which reached 110 hp. and 156Nm, respectively. The 7A FE engine was produced at the main production of Toyota Corporation from 1993 to 2002. Power units of the "A" series are still produced at some enterprises using license agreements.

Structurally, the power unit is made according to the in-line scheme of a gasoline four with two overhead camshafts, respectively, the camshafts control the operation of 16 valves. The fuel system is made of injection with electronic control and distributor distribution of ignition. Timing belt drive. When the belt breaks, the valves do not bend. The block head is made similar to the block head of the 4A series engines.

There are no official options for refinement and development of the power unit. Supplied with a single number-letter index 7A-FE to complete various vehicles until 2002. The successor to the 1800 cc drive appeared in 1998 and had the index 1ZZ.

Design improvements

The engine received a block with an increased vertical size, a modified crankshaft, a cylinder head, the piston stroke increased while maintaining the diameter.

The uniqueness of the design of the 7A engine is the use of a two-layer metal head gasket and a double-case crankcase. The upper part of the crankcase, made of aluminum alloy, was attached to the block and the gearbox housing.

The lower part of the crankcase was made of steel sheet, and made it possible to dismantle it without removing the engine during maintenance. The 7A motor has improved pistons. In the groove of the oil scraper ring there are 8 holes for draining oil into the crankcase.

The upper part of the cylinder block for fasteners is made similar to the ICE 4A-FE, which allows the use of a cylinder head from a smaller engine. On the other hand, the block heads are not exactly identical, as the intake valve diameters have been changed from 30.0 to 31.0 mm on the 7A series, while the exhaust valve diameter has been left unchanged.

At the same time, other camshafts provide a larger intake and exhaust valve opening of 7.6 mm versus 6.6 mm on a 1600 cc engine.

Changes were made to the design of the exhaust manifold to attach the WU-TWC converter.

Since 1993, the fuel injection system has changed on the engine. Instead of single-stage injection into all cylinders, they began to use paired injection. Changes were made to the settings of the gas distribution mechanism. The opening phase of the exhaust valves and the closing phase of the intake and exhaust valves have been changed. That allowed to increase power and reduce fuel consumption.

Until 1993, the engines used the cold injection system used on the 4A series, but then, after the cooling system was finalized, this scheme was abandoned. The engine control unit remains the same, with the exception of two additional options: the ability to test the operation of the system and knock control, which were added to the ECM for the 1800 cc engine.

Specifications and reliability

The 7A-FE had different characteristics. The motor had 4 versions. As a basic configuration, a 115 hp engine was produced. and 149Nm of torque. The most powerful version of the internal combustion engine was produced for the Russian and Indonesian markets.

She had 120 hp. and 157 Nm. for the American market, a "clamped" version was also produced, which produced only 110 hp, but with torque increased to 156 Nm. The weakest version of the engine produced 105 hp, just like the 1.6 liter engine.

Some engines are designated 7a fe lean burn or 7A-FE LB. This means that the engine is equipped with a lean-burn combustion system, which first appeared on Toyota engines in 1984 and was hidden under the acronym T-LCS.

LinBen technology made it possible to reduce fuel consumption by 3-4% when driving in the city and a little more than 10% when driving on the highway. But this same system reduced the maximum power and torque, so the evaluation of the effectiveness of this design improvement is twofold.

LB-equipped engines have been installed in Toyota Carina, Caldina, Corona and Avensis. Corolla cars have never been equipped with engines with such a fuel economy system.

In general, the power unit is quite reliable and not whimsical in operation. The resource before the first overhaul exceeds 300,000 km. During operation, it is necessary to pay attention to electronic devices serving the engines.

The overall picture is spoiled by the LinBurn system, which is very picky about the quality of gasoline and has an increased cost of operation - for example, it requires spark plugs with platinum inserts.

Main malfunctions

The main malfunctions of the engine are related to the functioning of the ignition system. The distributor spark supply system implies wear on the bearings of the distributor and gearing. As wear accumulates, spark timing can shift, resulting in either a misfire or loss of power.

High-voltage wires are very demanding on cleanliness. The presence of contamination causes a spark breakdown along the outer part of the wire, which also leads to engine tripping. Another cause of tripping is worn or dirty spark plugs.

Moreover, the operation of the system is affected by carbon deposits formed when using flooded or iron-sulphurous fuel, and external contamination of the surfaces of the candles, which leads to a breakdown on the cylinder head housing.

The malfunction is eliminated by replacing the candles and high-voltage wires in the kit.

As a malfunction, freezing of engines equipped with the LeanBurn system in the region of 3000 rpm is often recorded. The malfunction occurs because there is no spark in one of the cylinders. Usually caused by wear on the platinum swivel.

With a new high voltage kit, it may be necessary to clean the fuel system to remove contaminants and restore injector function. If this does not help, then the malfunction can be found in the ECM, which may require a flashing or replacement.

Engine knock is due to the operation of valves that require periodic adjustment. (At least 90,000 km). The piston pins in 7A engines are pressed in, so an additional knock from this engine element is extremely rare.

Increased oil consumption is built into the design. The technical passport of the 7A FE engine indicates the possibility of a natural consumption in operation of up to 1 liter of engine oil per 1000 kilometers.

Maintenance and technical fluids

The manufacturer indicates gasoline with an octane number of at least 92 as the recommended fuel. The technological difference in determining the octane number according to Japanese standards and GOST requirements should be taken into account. Unleaded 95 fuel may be used.

Engine oil is selected by viscosity in accordance with the mode of operation of the car and the climatic features of the region of operation. Synthetic oil of viscosity SAE 5W50 most fully covers all possible conditions, however, for everyday average operation, 5W30 or 5W40 viscosity oil is sufficient.

For a more precise definition, please refer to the instruction manual. The capacity of the oil system is 3.7 liters. When replacing with a filter change, up to 300 ml of lubricant may remain on the walls of the internal channels of the engine.

Engine maintenance is recommended every 10,000 km. In case of heavily loaded operation, or use of the car in mountainous areas, as well as with more than 50 engine starts at temperatures below -15 ° C, it is recommended to halve the service period.

The air filter is changed according to the state, but at least 30,000 km of run. The timing belt requires replacement, regardless of its condition, every 90,000 km.

N.B. When undergoing maintenance, a reconciliation of the engine series may be required. The engine number should be on the platform located at the rear of the engine under the exhaust manifold at the level of the generator. Access to this area is possible using a mirror.

Tuning and refinement of the 7A engine

The fact that the internal combustion engine was originally designed on the basis of the 4A series allows you to use the block head from a smaller engine and modify the 7A-FE engine to 7A-GE. Such a replacement will give an increase of 20 horses. When performing such a refinement, it is also desirable to replace the original oil pump on the unit from 4A-GE, which has a higher capacity.

Turbocharging of 7A series engines is allowed, but leads to a decrease in resource. Special crankshafts and liners for supercharging are not available.

The most common and most widely repaired of Japanese engines is the (4,5,7)A-FE series engines. Even a novice mechanic, diagnostician knows about the possible problems of the engines of this series. I will try to highlight (collect into a single whole) the problems of these engines. There are not many of them, but they bring a lot of trouble to their owners.

Sensors.

Oxygen sensor - Lambda probe.

"Oxygen sensor" - used to detect oxygen in the exhaust gases. Its role is invaluable in the process of fuel correction. Read more about sensor problems in article.

Many owners turn to diagnostics for the reason increased fuel consumption. One of the reasons is a banal break in the heater in the oxygen sensor. The error is fixed by the control unit code number 21. The heater can be checked with a conventional tester on the sensor contacts (R- 14 Ohm). Fuel consumption increases due to the lack of fuel correction during warm-up. You will not succeed in restoring the heater - only replacing the sensor will help. The cost of a new sensor is high, and it makes no sense to install a used one (their operating time is large, so this is a lottery). In such a situation, as an alternative, no less reliable universal sensors NTK, Bosch or original Denso can be installed.

The quality of the sensors is not inferior to the original, and the price is much lower. The only problem may be the correct connection of the sensor leads. When the sensor sensitivity decreases, fuel consumption also increases (by 1-3 liters). The operability of the sensor is checked by an oscilloscope on the diagnostic connector block, or directly on the sensor chip (number of switching). The sensitivity drops when the sensor is poisoned (contaminated) with combustion products.

Engine temperature sensor.

"Temperature sensor" is used to register the temperature of the motor. If the sensor does not work correctly, the owner will have a lot of problems. If the measuring element of the sensor breaks, the control unit replaces the sensor readings and fixes its value by 80 degrees and fixes error 22. The engine, with such a malfunction, will operate normally, but only while the engine is warm. As soon as the engine cools down, it will be problematic to start it without doping, due to the short opening time of the injectors. There are frequent cases when the resistance of the sensor changes randomly when the engine is running at H.X. - the revolutions will float in this case. This defect is easy to fix on the scanner, observing the temperature reading. On a warm engine, it should be stable and not randomly change values from 20 to 100 degrees.

With such a defect in the sensor, a “black caustic exhaust” is possible, unstable operation on H.X. and, as a result, increased consumption, as well as the inability to start a warm engine. It will be possible to start the engine only after 10 minutes of sludge. If there is no complete confidence in the correct operation of the sensor, its readings can be replaced by including a 1 kΩ variable resistor or a constant 300 ohm resistor in its circuit for further verification. By changing the readings of the sensor, the change in speed at different temperatures is easily controlled.

Throttle position sensor.

The throttle position sensor tells the on-board computer what position the throttle is in.

A lot of cars went through the assembly disassembly procedure. These are the so-called "constructors". When removing the engine in the field and subsequent assembly, the sensors suffered, on which the engine is often leaned. When the TPS sensor breaks, the engine stops throttling normally. The engine bogs down when revving. The machine switches incorrectly. Error 41 is fixed by the control unit. When replacing a new sensor, it must be adjusted so that the control unit correctly sees the sign of X.X., with the gas pedal fully released (throttle closed). If there is no sign of idling, adequate X.X control will not be carried out, and there will be no forced idling mode during engine braking, which again will entail increased fuel consumption. On engines 4A, 7A, the sensor does not require adjustment, it is installed without the possibility of rotation-adjustment. However, in practice, there are frequent cases of bending the petal, which moves the sensor core. In this case, there is no sign of x / x. The correct position can be adjusted using a tester without using a scanner - on the basis of idling.

THROTTLE POSITION……0%
IDLE SIGNAL……………….ON

MAP absolute pressure sensor

The pressure sensor shows the computer the real vacuum in the manifold, according to its readings, the composition of the fuel mixture is formed.

This sensor is the most reliable of all installed on Japanese cars. His resilience is simply amazing. But it also has a lot of problems, mainly due to improper assembly. They either break the receiving “nipple”, and then seal any passage of air with glue, or violate the tightness of the inlet tube. With such a break, fuel consumption increases, the level of CO in the exhaust rises sharply up to 3%. It is very easy to observe the operation of the sensor on the scanner. The line INTAKE MANIFOLD shows the vacuum in the intake manifold, which is measured by the MAP sensor. If the wiring is broken, the ECU registers error 31. At the same time, the opening time of the injectors sharply increases to 3.5-5ms. When regassing, a black exhaust appears, the candles are planted, shaking appears on H.X. and stop the engine.

Knock sensor.

The sensor is installed to register detonation knocks (explosions) and indirectly serves as a "corrector" of the ignition timing.

The recording element of the sensor is a piezoelectric plate. In the event of a sensor malfunction, or a break in the wiring, at over 3.5-4 tons of revs, the ECU fixes error 52. Sluggishness is observed during acceleration. You can check the performance with an oscilloscope, or by measuring the resistance between the sensor output and the housing (if there is resistance, the sensor needs to be replaced).

crankshaft sensor.

The crankshaft sensor generates pulses, from which the computer calculates the speed of rotation of the engine crankshaft. This is the main sensor by which the entire operation of the motor is synchronized.

On 7A series engines, a crankshaft sensor is installed. A conventional inductive sensor is similar to the ABC sensor and is practically trouble-free in operation. But there are also confusions. With an interturn circuit inside the winding, the generation of pulses at a certain speed is disrupted. This manifests itself as a limitation of engine speed in the range of 3.5-4 tons of revolutions. A kind of cut-off, only at low speeds. It is quite difficult to detect an interturn circuit. The oscilloscope does not show a decrease in the amplitude of the pulses or a change in frequency (during acceleration), and it is rather difficult for a tester to notice changes in Ohm's shares. If you experience symptoms of speed limit at 3-4 thousand, simply replace the sensor with a known good one. In addition, a lot of trouble causes damage to the master ring, which mechanics break when replacing the front crankshaft oil seal or timing belt. Having broken the teeth of the crown, and restored them by welding, they achieve only a visible absence of damage. At the same time, the crankshaft position sensor ceases to adequately read information, the ignition timing begins to change randomly, which leads to loss of power, unstable engine operation and increased fuel consumption.

Injectors (nozzles).

Injectors are solenoid valves that inject pressurized fuel into the engine's intake manifold. Controls the operation of the injectors - the engine computer.

Idle valve.IAC

The valve is responsible for engine speed in all modes (warm-up, idling, load).

During operation, the valve petal becomes dirty and the stem is wedged. Turnovers hang on warming up or on X.X. (due to the wedge). Tests for changes in speed in scanners during diagnostics for this motor are not provided. The performance of the valve can be assessed by changing the readings of the temperature sensor. Enter the engine in the "cold" mode. Or, having removed the winding from the valve, twist the valve magnet with your hands. Jamming and wedge will be felt immediately. If it is impossible to easily dismantle the valve winding (for example, on the GE series), you can check its operability by connecting to one of the control outputs and measuring the duty cycle of the pulses, while simultaneously controlling the speed of X.X. and changing the load on the engine. On a fully warmed-up engine, the duty cycle is approximately 40%, by changing the load (including electrical consumers), an adequate increase in speed in response to a change in duty cycle can be estimated. When the valve is mechanically jammed, a smooth increase in the duty cycle occurs, which does not entail a change in the speed of H.X. You can restore work by cleaning soot and dirt with a carburetor cleaner with the winding removed. Further adjustment of the valve is to set the speed X.X. On a fully warmed up engine, by rotating the winding on the mounting bolts, they achieve tabular revolutions for this type of car (according to the tag on the hood). Having previously installed the jumper E1-TE1 in the diagnostic block. On the “younger” 4A, 7A engines, the valve has been changed. Instead of the usual two windings, a microcircuit was installed in the body of the valve winding. We changed the valve power supply and the color of the winding plastic (black). It is already pointless to measure the resistance of the windings at the terminals. The valve is supplied with power and a control signal of a rectangular shape with a variable duty cycle. To make it impossible to remove the winding, non-standard fasteners were installed. But the problem of the stem wedge remained. Now, if you clean it with an ordinary cleaner, the grease is washed out of the bearings (the further result is predictable, the same wedge, but already because of the bearing). It is necessary to completely dismantle the valve from the throttle body and then carefully flush the stem with the petal.

Ignition system. Candles.

Because of them, sparking will not be inside the cylinder, but outside it. With smooth throttling, the engine runs stably, and with a sharp one, it crushes. In this situation, it is necessary to replace both the candles and the wires at the same time. But sometimes (in the field), if replacement is impossible, you can solve the problem with an ordinary knife and a piece of emery stone (fine fraction). With a knife we cut off the conductive path in the wire, and with a stone we remove the strip from the ceramics of the candle. It should be noted that it is impossible to remove the rubber band from the wire, this will lead to the complete inoperability of the cylinder.
Another problem is related to the incorrect procedure for replacing candles. The wires are pulled out of the wells with force, tearing off the metal tip of the rein. With such a wire, misfiring and floating revolutions are observed. When diagnosing the ignition system, you should always check the performance of the ignition coil on the high-voltage arrester. The simplest test is to look at the spark gap on the spark gap with the engine running.

If the spark disappears or becomes filiform, this indicates an inter-turn short circuit in the coil or a problem in the high voltage wires. A wire break is checked with a resistance tester. A small wire is 2-3k, then a long 10-12k is further increased. The resistance of a closed coil can also be checked with a tester. The resistance of the secondary winding of the broken coil will be less than 12 kΩ.

Coils of the next generation (remote) do not suffer from such ailments (4A.7A), their failure is minimal. Proper cooling and wire thickness eliminated this problem.

Another problem is the current oil seal in the distributor. Oil, falling on the sensors, corrodes the insulation. And when exposed to high voltage, the slider is oxidized (covered with a green coating). The coal turns sour. All this leads to disruption of sparking. In motion, chaotic shootings are observed (into the intake manifold, into the muffler) and crushing.

Subtle faults

On modern 4A, 7A engines, the Japanese have changed the firmware of the control unit (apparently for faster engine warm-up). The change is that the engine reaches idle speed only at 85 degrees. The design of the engine cooling system was also changed. Now a small cooling circle intensively passes through the head of the block (not through the pipe behind the engine, as it was before). Of course, the cooling of the head has become more efficient, and the engine as a whole has become more efficient. But in winter, with such cooling during movement, the temperature of the engine reaches a temperature of 75-80 degrees. And as a result, constant warm-up revolutions (1100-1300), increased fuel consumption and nervousness of the owners. You can deal with this problem by either insulating the engine more, or by changing the resistance of the temperature sensor (deceiving the computer), or by replacing the thermostat for the winter with a higher opening temperature.
Oil
Owners pour oil into the engine indiscriminately, without thinking about the consequences. Few people understand that different types of oils are not compatible and, when mixed, form an insoluble porridge (coke), which leads to the complete destruction of the engine.

The most inexpensive and easily accessible element is the air filter. Owners very often forget about replacing it, without thinking about the likely increase in fuel consumption. Often, due to a clogged filter, the combustion chamber is very heavily polluted with burnt oil deposits, valves and candles are heavily contaminated. When diagnosing, it can be erroneously assumed that the wear of the valve stem seals is to blame, but the root cause is a clogged air filter, which increases the vacuum in the intake manifold when contaminated. Of course, in this case, the caps will also have to be changed.
Some owners do not even notice that garage rodents live in the air filter housing. Which speaks of their complete disregard for the car.

The fuel filter also deserves attention. If it is not replaced in time (15-20 thousand mileage), the pump starts to work with overload, the pressure drops, and as a result, it becomes necessary to replace the pump. The plastic parts of the pump impeller and check valve wear out prematurely.

The pressure drops. It should be noted that the operation of the motor is possible at a pressure of up to 1.5 kg (with a standard 2.4-2.7 kg). At reduced pressure, there are constant shots into the intake manifold, the start is problematic (after). Significantly reduced traction. It is correct to check the pressure with a pressure gauge (access to the filter is not difficult). In the field, you can use the "return filling test". If, when the engine is running, less than one liter flows out of the gasoline return hose in 30 seconds, it can be judged that the pressure is low. You can use an ammeter to indirectly determine the performance of the pump. If the current consumed by the pump is less than 4 amperes, then the pressure is squandered. You can measure the current on the diagnostic block.

When using a modern tool, the process of replacing the filter takes no more than half an hour. Previously, this took a lot of time. Mechanics always hoped in case they were lucky and the bottom fitting did not rust. But often that is what happened. I had to rack my brains for a long time, with which gas wrench to hook the rolled-up nut of the lower fitting. And sometimes the process of replacing the filter turned into a “movie show” with the removal of the tube leading to the filter. Today, no one is afraid to make this change.

Control block.

Until the year 98, control units did not have sufficiently serious problems during operation. The blocks had to be repaired only because of a hard polarity reversal. It is important to note that all conclusions of the control unit are signed. It is easy to find on the board the necessary sensor output to check or continuity of the wire. The parts are reliable and stable in operation at low temperatures.

In conclusion, I would like to dwell a little on gas distribution. Many “hands on” owners perform the belt replacement procedure on their own (although this is not correct, they cannot properly tighten the crankshaft pulley). Mechanics make a quality replacement within two hours (maximum). If the belt breaks, the valves do not meet the piston and fatal destruction of the engine does not occur. Everything is calculated to the smallest detail.
We tried to talk about the most common problems on the engines of this series. The engine is very simple and reliable, and subject to very tough operation on "water - iron gasoline" and dusty roads of our great and mighty Motherland and the "maybe" mentality of the owners. Having endured all the bullying, to this day he continues to delight with his reliable and stable work, having won the status of the most reliable Japanese engine.
Vladimir Bekrenev, Khabarovsk.
Andrey Fedorov, Novosibirsk.

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(Lean Bum) refers to low-speed power units, characterized by a high degree of traction. In serial production, such engines were calculated for installation in Japanese passenger cars of the Corolla family. A little later, these power units found their way into the Caldina, Carina line of cars, and were equipped with a Lean Bum power system, which works very well with lean fuel mixtures, which, to a large extent, raised the level of fuel economy of cars designed for constant movement in conditions of the city, associated with frequent standing in traffic jams.

Unfortunately, after the appearance of Japanese cars in which engine 7a, on the territory of the post-Soviet space, one could hear frequent complaints about the inadequate operation of the mentioned fuel system, which manifests itself in gas pedal failures, especially at medium engine speeds. To establish the exact cause of what is happening, sometimes, even experts do not undertake. Some say that the poor quality of the fuel used is to blame, others blame the car ignition and power systems for what is happening, which in these vehicles are very sensitive to the technical condition of the spark plugs and high-voltage wires. One way or another, but in practice there are cases when the lean fuel mixture simply did not ignite.

In addition to the above, the disadvantages of 7a engines include difficulties in adjusting the intake valves, piston pins that do not “float”, and premature wear of the camshafts. Although, in general, the power unit is 7a, the device is quite reliable and easy to operate, maintain, and repair.

Engine 7a refers to engines of a later modification, having an increased working volume, in comparison with power units 4a and 5a (FE). Its distinguishing feature is very good mechanics. It is quite maintainable, and this unit has never had problems with spare parts. Very often, malfunctions in the operation of power units 7a occur due to the failure of any of the numerous sensors. Particular attention should be paid to the oxygen sensor, engine temperature sensor, and throttle sensor. When replacing them, it is recommended to install only original devices, in particular Denso, although Bosch, NTK products are also suitable.