Air leakage in the engine leads to unstable, high idle speed and unstable engine operation in transient conditions. Consider the places of possible suction and how to determine it in garage conditions.
In order to maintain the composition of the TPVA in the stoichiometry of the engine ECU, it is necessary to know exactly the amount of air entering the intake manifold. Additional air, which cannot be compensated by the idle speed control system, leads to malfunctions of the internal combustion engine.
Air leak symptoms
- Unstable idling (the tachometer needle either rises or falls).
- Too high idle.
- High heating speeds. At the end of the warm-up period, the revolutions constantly rise and fall sharply (sawtooth jumps). In such cases, they also say that the engine ECU “cuts” idling.
- Cold start is worse.
- Fuel consumption increases.
Start by studying the design features of the fuel injection system on your car. First of all, pay attention to the method of calculating air and the type of idle control system. On modern gasoline ICEs, the calculation is based on the readings of the MAF-sensor (DMRV) or MAP-sensor (DAD) + Air Temperature Sensor (DTV). Maintaining and adjusting idle speed is carried out by the IAC valve or by turning the throttle valve by a small angle. Understanding the processes and how to control them will help you quickly find air leaks in the engine.
Possible causes of air leakage
- Torn, loosely screwed pipe from the air filter to the intake manifold. Due to vibrations, the pipe most often cracks in the corrugated part.
- Frayed, cut, cracked hoses of the vacuum system. Carefully inspect all hoses coming from the intake manifold.
- Torn diaphragm of the vacuum brake booster, leaky housing of the vacuum cleaner, non-return valve. With such a malfunction, the character of the engine changes when the brakes are pressed, and the pedal itself becomes stiffer.
- Cracked housing of the oil separator of the crankcase ventilation system, wedged or stuck in the open position of the PCV valve, purge valve of the fuel tank adsorber.
- Air leak through the sealing rings of the injectors.
- Adhesion of dirt, varnish deposits, soot, inside the throttle, due to which the damper does not close completely. On a car with TPS, the actual position of the damper can be tracked with a diagnostic tool, so it is not necessary to disassemble the intake tract.
- Cracked intake manifold, leaky connection between the manifold and the cylinder head.
- Faulty, clogged IAC valve. If the valve causes the calibration hole to be larger than the base value, excess air will enter the engine at idle.
- Suction through the gap between the throttle axis and its seat (appears due to wear of the rubbing pairs).
The most characteristic places for air leakage in an injection engine are described above. If all of them have been checked, pay attention to the design features of your car. For example, on many Hondas of the early 90s, there is a fast idle valve in the idle control system. Vacuum tubes do not go to it, so it is not so easy to understand its purpose and method of verification on the go. In the case of a torn membrane, unaccounted air is sucked in. As a result, the ECU “saws” idling, the engine almost stalls after regassing.
Methods for determining
- Listen to the intake tract at the gas lines. Often, the place of suction can be localized by the characteristic curling, hissing sound of the air being sucked in.
- Alternately pinch all the hoses suitable for the intake manifold with tongs. A change in the operation of the engine indicates that air leakage is located precisely in the pinched circuit. Inspect hoses, valves and other vacuum consumers that are included in the system.
- Use the smoke generator. There are enough ready-made solutions on the Internet that allow you to assemble a smoke generator with your own hands for little money.
- Spray carburetor/brake cleaner, contact cleaner, or other flammable ester-based fluid near suspected leaks. Getting into the manifold through the place of suction, the liquid will enrich the mixture and a temporary jump in speed. At the time of the test, it will be useful to observe the signal of the lambda probe.
Attention! This method of searching for suction is extremely fire hazardous! Do not spray cleaners, quick start, near the exhaust manifold. Dot the composition in small doses.
Computer diagnostics
The engine ECU is not able to recognize the air leak and give an error with a clear wording. An indirect symptom may be a lean mixture code, a malfunction of the idle control system, vacuum valves. But one should not rush to conclusions, relying only on self-diagnosis.
It is much more important when looking for leaks in real time to observe the behavior of the IAC valve, throttle position sensor, short-term and long-term correction. If the suction is small, the engine ECU increases the duration of injection, returning the mixture to stoichiometric. The engine will start to run smoothly, but after removing the errors, problems with idling will again manifest themselves. This happens due to the zeroing of short-term and long-term fuel corrections.
The cause of sawtooth jumps can also be tracked by a diagnostic scanner. Watching the opening time of the injectors, you will see that when a certain number of revolutions is reached, the injectors simply turn off. This happens due to the fact that the ECU, when air is leaking, may think that the car is rolling in gear from a hill. He understands this by the increased air consumption (the damper is closed, and the desired and actual position of the IAC valve coincide). Write to me, please, on the soap indicated in the autoburum profiles. Therefore, to save fuel, the ECU turns off the injectors.
Consider one of the easiest ways to check air leakage in the intake manifold of an injection car without any material costs.
This method is not a panacea, but is the simplest and most effective in finding air leaks in the intake manifold.
As you know, during engine operation, a large vacuum is created in the manifold. At idle, the pressure in the manifold drops to 30 kPa, and atmospheric pressure is usually around 100 kPa.
Such a pressure difference forces the air from outside the collector to get inside the collector by all available paths. If he succeeds, then you should not even think about the normal operation of the engine - all kinds of jerks and dips, as well as excessive fuel consumption are provided!
So our task with you is to find all these “accessible ways” for the penetration of unaccounted air into the intake manifold.
The main symptoms of air leakage are:
- increased idle speed
- floating idle speed
- inadequate response of the engine to pressing / releasing the gas pedal
- increased fuel consumption
The simplest and most effective method of checking for air leaks into the intake manifold is to fill the manifold with low pressure smoke. And if there are leaks in the collector, then they can be seen by the smoke coming out of them.
For these purposes, smoke generators are used. But not all service stations have such equipment, and it is somehow expensive to buy it for yourself to use it once every two or three years. How to be?
You can do as I did - collect a free smoke generator "on your knee" from plastic bottles.
In general, I was standing at the checkpoint the other day. And in order not to waste time in vain, I decided to bring to life an idea that had been worrying me for a long time - to assemble a simple smoke generator to check the intake manifold.
From a suitable tool, I found only a small knife and a triangular file without a handle.
A one and a half liter plastic bottle was also freed from water down the throat. I also bought a half liter bottle of a certain drink, which was quickly drained by my daughter
First of all, I cut a large and a small bottle into two parts. I threw away the top of the small bottle. In total, there are two lower parts (small and large) and one upper. I think it's understandable.
Removed the hose from the crankcase ventilation valve. I made a hole in the bottle cap with a file so that the removed hose entered it with effort. I screwed the top of a large bottle onto the cap. Here is a picture
From a different angle
Everything turned out tight
Then he dug a hole in the bottoms of both lower parts. In the smaller one, under the diameter of the cigarette, and in the upper one, under the diameter, the hoses from the compressor for pumping the wheels.
He shot a cigarette from the driver of a neighboring car, lit it and inserted it into the hole of a smaller bottle, and shoved the whole thing upside down into a large bottle
I put it all in the top of the bottle and connected the car compressor
Here is a general view of this constructor
The appearance of such a problem for any driver is always unexpected and unpleasant. Immediately before the owner, several questions arise about what happened to the car, where to look for a malfunction, how to fix it. Most drivers will seek help from specialists or "experts", although in many cases troubleshooting can be done on your own.
A little about the symptoms of a malfunction
The power unit of a car is a complex engineering structure. If, after detecting even small deviations in its work, you should deal with the problem that has arisen and eliminate it. If this is left unattended, you can wait for the occurrence of major complications, which will entail not only significant material costs, but also moral costs, a long downtime of the machine.
What happens when air leaks appear on the VAZ 2112, 2114 or other models? A number of symptoms may indicate the appearance of such a malfunction:
- Difficulty starting the engine after a long stop;
- The idle speed of the motor "floats";
- Engine power is lost;
- Fuel consumption increases.
Floating idle speed can cause the engine to stall. If this happened at an intersection, and besides, the engine does not start well, this is already creating a traffic jam, nervousness of other road users, and there are prerequisites for creating an emergency. If the car is equipped with a power unit with a carburetor, an attempt to adjust the idle speed with the screws for the quantity and quality of the fuel mixture will not lead to success.
This is prevented by the appeared air leakage, going past the idle channels. The loss of power indicators of the motor will become noticeable. The car loses its agility, driving at low speeds has a long period. The movement can only be started at increased speeds. Vehicles with injection engines that are equipped with sensors that monitor mass fuel consumption will experience too low idle. The on-board computer may show a lambda probe failure. A lean fuel mixture will not allow you to get maximum torque, frequent misfires of the mixture in the cylinders become noticeable. Driving in the usual mode will lead to increased fuel consumption.
Advice! If you notice the appearance of these signs, stop the car and carefully inspect the engine compartment. The cause of the failure may be a loose hose clamp, or other similar “little thing”.
How to find a problem area
Sometimes this may take only a few minutes, in other cases a rather long period. In addition to the manifestation of these symptoms, the occurrence of a malfunction can be indicated by the on-board computer with the “lean mixture” signal. Detecting air leaks in a VAZ 2112, 2114 power unit is not as easy as it might seem at first glance. There are several different ways to perform this operation. In this article, we will look at them in more detail.
The entry of an "extra" mixture is possible at the joints and seals in the intake tract of the motor. This fully applies to all hoses, gaskets, injectors, throttle valves, sensors, and other intake manifold assemblies. There have been cases when the gasket between the head and the cylinder block became the culprit of this phenomenon. First of all, disconnect the MRV sensor. After that, start the engine, and close the entrance with a flat object. The motor must stop, otherwise there is a "hole".
Try spraying plain water on problem areas. It can close the hole that has appeared for a short time, which will lead to a slight decrease in speed. Instead of water, you can do the same procedure with ether. In this case, the turnover should increase. It is not always possible to find the passage of an excess mixture of a VAZ power unit by such methods, so mechanics use other methods. Reputable automotive centers in such cases simply measure the intake manifold vacuum. To do this, they have special measuring instruments. They are commercially available, but it is not economically feasible to purchase them for single use.
What is the driver to do? Effective assistance in finding places for air leaks VAZ 2112, 2114 is provided by steam generators, smoke generators. They have a simple design and are easy to assemble at home. The process of describing their manufacture can be easily found on the Internet, so we will not dwell on this. Let's take a closer look at their use. Any, even the slightest violation of tightness, can be detected by the streams of smoke that form in the smoke generator.
To quickly find the "hole" you need to correctly connect the outlet of the smoke source to the intake tract. The most suitable place for many mechanics is the place where the hose from the brake booster is connected. Serve the smoke mixture and try to find leaks in the joints. In most cases, this turns out to be the most effective method.
A few words about troubleshooting
It was possible to find air leakage in the VAZ 2112, 2114 engine, now it should be eliminated. The algorithm for fixing the problem will be different, depending on the place of the pass. If clamps are the culprit, they are tightened. If this is not possible due to the hardness of the rubber pipes, it is better to replace them with new ones. Leaky gaskets are also replaced with new ones. In some cases, this can be a time-consuming process, such as when replacing the gasket between the head and cylinder block.
For this, desire alone is not enough, since it will require the use of a torque wrench to tighten the block head bolts, a diagram of their installation and screwing. After a short run, they will have to be “pressed” again. It will be a little easier to replace the intake tract gasket, but you will also have to dismantle and then reinstall a number of parts.
Advice! If such an operation is performed for the first time, write down the order in which components and parts are removed. This will make it easier to install them during assembly.
Cases were noted by mechanics when the VAZ 2112, 2114 power units had air leaks in the fuel rail. For some reason, VAZ manufacturers install a rubber hose crimped with two clamps in the fuel supply system. Re-compressing them usually fixes the problem. Most often, replacing "outdated" rubber products in the intake tract solves all the problems that have arisen.
It is much more difficult to troubleshoot intake tract sensors such as MRV, idle, idle speed controller. This is not about replacing gaskets, but about sensor malfunctions, due to which air leakage in the motors is possible. The craftsmen do not undertake to eliminate air leakage in these devices, they simply change them with new ones. Repair of conductive tracks, elimination of pollution or oxidation is possible. The appearance of air leakage in VAZ vehicles in the fuel system is accompanied by the presence of leaks.
Important! Ignoring the driver of a fuel leak that has appeared threatens to cause a fire.
This may be the junction of the electric fuel pump with the fuel line, the fuel pressure regulator, in other places. Before starting work immediately after stopping the engine, relieve pressure in the fuel system. Otherwise, fuel may be ejected and ignited.
If you let the car stand for a while, the pressure will drop on its own. Another place where a malfunction may be located can be the nozzles of the power unit. To be precise, it's not a nozzle, but a gasket between it and the block head. These damaged parts are not particularly scarce, they can be easily bought in retail chains, so they are simply changed. If the nozzles are dismantled, and the car has a solid mileage, it makes sense to flush them. This procedure is quite doable in the garage with your own hands.
This article is not a direct guide to action, it is for informational purposes only. It is difficult to describe all the possible causes of the problem and how to fix them. If readers have questions, watch the video.
Not only the maximum engine power depends on the composition of the air-fuel mixture (its “quality”), but, what is sometimes more important, its controllability - excess air entering the intake tract can cause the engine to stop at the most inopportune moment. Let's say you're leaving a secondary road for a main one. We estimated the distance to the flow of cars moving along the main road - and when you try to “take off”, the engine stalls ... Damage to the car from a side impact may not be the most serious consequence in this case.
What could be the symptoms of air leakage in the intake manifold and “how to deal with them” is the topic of this article.
Insignificant "surpluses" of air may not manifest themselves in any way, since they are not capable of greatly changing the composition of the combustible mixture, and only engine diagnostics can detect them.
But with major damage to the intake tract, symptoms of air leakage can be:
The first symptom of air leakage in the intake tract is the unstable idling of the engine.
- unstable operation of the engine at idle, up to its stop;
- failures during acceleration, and when you sharply press the “gas” pedal, the engine may stall again, especially at the beginning of the car;
- an increase in the operating temperature of the motor is possible due to its operation on a too lean mixture.
It should be noted that the uneven operation of the engine is “smoothed out” at medium and high speeds, one can only note a decrease in the traction qualities of the engine.
How can "extra" air enter the cylinders?
The ingress of excess air into the fuel mixture is possible not only directly through a violation of the intake manifold gasket, but also through the parts associated with it. Let us consider in more detail the possible places of violation of the integrity of the intake tract for carburetor and injection engines separately.
carbureted engine
Possible places for air leakage at the intake
Possible "weaknesses":
A common cause of air leakage is deformation of the "sole" of the carburetor when the carburetor is tightened on a hot engine.
- gasket for the carburetor;
- carburetor diaphragm. Basically, these are the diaphragms of the trigger and the actuator of the shutter of the second chamber - not all models have the latter;
- vacuum hoses for controlling the advance angle (goes to the distributor), for all kinds of pneumatic valves; also sometimes the carburetor fittings themselves are loosely inserted into the body at the factory;
- deformation of the "sole" of the carburetor; a very common cause of suction, caused by the fact that the carburetor is tightened on a hot engine.
injection engine
Suction is possible through:
- nozzle seals;
- receiver gasket;
Generalization
In addition, for both types of engines, suction is possible through a damaged hose of the vacuum brake booster, as well as through the seal of its valve (fitting) inserted into the booster housing. Moreover, many motorists ignore the fact that if the free play of the brake light switch (“frog”) is incorrectly set, the correct operation of the amplifier itself can be disrupted, as a result of which the air intake from it will be “wrong”, which will cause excessive air intake into the intake collector. The correct setting of the "vacuum" is also affected by the amount of protrusion of its rod from the body. The most unpleasant thing in this situation is that air leakage "through" the vacuum booster cannot be detected from the outside during inspection.
Troubleshooting
You can easily and clearly determine the air leakage in the intake manifold with a smoke generator.
The most accessible way to find air leaks in the intake manifold is a visual inspection. Cracks and ruptures in air hoses can also be seen with the "naked" eye. You can also check how tightly the parts are connected to each other. It often happens that during the repair, for example, the nuts of the carburetor or other components were not tightened properly.
If there are no visible causes of malfunctions, then it is very effective to spray from a can of "Quick Start" compositions made on the basis of ether along the joints of the parts. The procedure must be carried out with the engine running. The ether that has entered the collector through the slots will cause changes in the operation of the motor - its speed should increase for a short time.
Finally, the question of how you can detect air leaks in the intake manifold is easy to resolve if you have a smoke generator. With its help, the search for places of leaks does not present any particular problems. Having “pumped up” the intake tract with smoke, you can visually observe where the integrity of the intake system is violated - in this case, it is better to use a blue lamp (flashlight) - it becomes more noticeable in its light.
Elimination of air leakage in the intake manifold
When repairing the intake manifold, do not apply force to the sensors - excessive force can damage them.
Repair, basically, is reduced to the replacement of gaskets, seals and vacuum hoses. Moreover, it is not necessary to restore cracked hoses with a sealant - its excess, once in the air path, can cause blockages.
When repairing, remember that you should not put effort on trying to check if some of them are jammed. This is especially true of the idle speed controller - it is just installed in the intake tract. By pressing on its core, you run the risk of completely spoiling the regulator, which is a stepper motor.
And finally - keep in mind one more important point. Sometimes air leakage "from the side", although it does not affect the operation of the engine in any way, can lead to very unpleasant consequences. We are talking about cases where air enters the manifold, bypassing the air filter. For example, if that part of the filter housing is split, from which the dust-free air enters the collector. It happens that a person drives for a long time with a fair crack in the filter housing or in the corrugated air intake hose from the filter to the throttle body. The idle speed and engine power will be normal, but you risk greatly reducing the resource of the motor itself.
An automobile magazine once published an article about an experiment carried out by a group of inquisitive people - they drove through the desert without an air filter. The engine completely "ended" without even passing 100 km. Therefore, look carefully!
A car is a complex mechanism in which everything must work perfectly. Otherwise, the risk of an accident increases significantly, moreover, one faulty part can lead to premature wear of the entire system. To prevent this from happening, you need to be attentive to your iron comrade and fix all malfunctions in time for their prompt elimination.
The engine is the heart of the car. Without its normal functioning, the very possibility of movement of the vehicle comes into question. A negative role in the operation of this unit is played by air leakage in the intake manifold. If this defect appears in your car, the engine can stall in the middle of the road.
Essence and symptoms
The essence of the malfunction
When there is a leak in the intake manifold, much more air begins to flow into the engine than it should. Naturally, this negatively affects the operation of the entire system.
Important! The result of the appearance of air leakage in the intake manifold is the depletion of the fuel-air mixture.
When this symptom is activated, the motor starts to work unstably. Depending on the severity of the breakdown, the list of possible symptoms can vary greatly. Therefore, it is not so easy to find a malfunction.
Symptoms of an engine leak
Over the years, car owners and automotive experts have compiled a list of symptoms that may indicate that the engine is sucking air through the intake manifold:
- At idle, the engine is unstable. With such a symptom, you simply cannot set the idle below the 1000 rpm mark. Each attempt will turn off the motor.
- Temperature changes. The engine will overheat frequently. Plus, it won't depend on the driving mode you choose.
- Difficulties when starting will be especially noticeable in the morning.
- At low speeds, the power of the motor will drop dramatically. At a mark of less than 2000 rpm, the car will not be able to accelerate.
- Fuel consumption will increase dramatically.
- When driving at 2000 rpm and more, there are no problems.
Each of these symptoms indicates that there is air leakage in the intake manifold. Therefore, if at least one of them is detected, it is necessary to conduct a detailed diagnosis and determine the malfunction.
We diagnose and fix leaks
Start the engine first. It must run at idle. After that, listen to the operation of the device. Very a characteristic hiss of air can often be heard.
Attention! By the source of the hiss, you can find a breakdown.
In some cases, it is not immediately possible to localize the source of noise. In this case, you will need to pinch the hoses that connect to the manifold. In most situations, problems are observed with the vacuum hose, which is responsible for boosting the brakes. But exceptions are possible.
Sometimes a power surge can be observed during the removal of the clamp. In this case, the problem lies precisely in this detail. Usually this indicates such malfunctions as:
- adsorber valve failure,
- failure of the vacuum booster,
- holes in the hose.
If after the manipulations the problem is still not detected, you must use the sprayer. Flammable liquid is poured into it. It is best to use special cleaners for carburetors.
In a thin stroke, spray liquid on potential places through which air is supposedly leaking into the intake manifold. With special care you need to process:
- cylinder head joint,
- collector joint,
- corrugation,
- receiver seams,
- throttle joint.
As soon as the liquid enters the damaged area, it will be drawn in and end up in the motor. In this case, you will observe a jump in revolutions.
The most efficient method
In order to use this technique for detecting air leaks in the manifold, you need to find a smoke generator. Next, select any opening in the intake tract and slowly begin to pump smoke through it into the system.
Attention! It is better to use engine oil as a consumable, it provides a large amount of smoke.
Next, to find the air leak in the intake manifold, take a halogen lamp. With its help, you can easily find wisps of smoke. For the procedure, you will need special adapters.
Troubleshooting
A lot depends on where you find the air leak in the manifold. For example, if the hole in the hose is small, you can use sealant and cover up the damage. Of course, ideally, the damaged element should be replaced. Very often this operation must be done with couplings, o-rings and gaskets.
Results
Air leakage through the intake manifold is easiest to diagnose using a smoke generator. The elimination of the defect directly depends on where exactly the breakdown was detected.
