And you can hardly enter the climb only in second gear? In this case, you may suspect a misfire. And if available, you can find out. In this case, the numbers next to the letter will indicate in which particular cylinder there are misfires: 0301 - in the first, 0302 - in the second, 0303 - in the third, 0304 - in the fourth. What is the problem?
Misfiring is a phenomenon that occurs in an engine when one cylinder accelerates more slowly than the others, thereby disrupting the duty cycle. As a result, the exhaust deteriorates, the car "twitches" and does not go.
In this case, there are two ways: visit a car service where qualified specialists will solve your problem, or try to fix misfires on your own. The reasons for the failure can be very different. In this article we will consider only the most common:
1. Due to the poor quality of the fuel, the nozzles are clogged. In this case, it is only necessary to replace the gas station or switch to high-octave gasoline. But it is worth knowing what may occur due to some breakdowns of the pressure regulator, fuel pump, or due to a clogged filter.
2. Perhaps your spark plugs are broken - with a large or small gap. They may also just be of poor quality.
3. with mechanical damage or high resistance can also cause misfiring.
4. Or a module that is out of order.
5. Low or uneven compression can result in insufficient compression of the mixture.
6. Misfire can also occur due to improper adjustment of timing gaps.
7. Leakage of hydraulic compensators.
8. Malfunction of any cylinder, which may occur, for example, due to a decrease in the gap between the internal combustion engine cylinder and the piston.
How to find the reason?
To some extent, the task is simplified if your car is equipped with "electronic brains". In this case, you can use autotesters that can immediately show error codes (misfires that occur in the first or third cylinder, for example). In addition, the autotester can also identify the direction of the search for the root cause. For example, code 0300 means a misfire that occurs in all cylinders. In this case, the cause is most likely a bad working mixture. And this means that the reasons may be as follows: low pressure due to a bad pump or too high air leakage.
If you do not have an electronic assistant, then you can find the cause in the old, time-tested ways. Start with the electrical equipment under the hood: high voltage, the condition of the fuel pump, measuring the compression in the cylinders. At the final stage, if misfiring is not eliminated, proceed to inspect the engine. Remove the cylinder head cover and diagnose the condition of the valve guides and rings.
For some ICE models, the camshaft is located in the cylinder head. In this case, the cylinder head must be removed to inspect the valve springs. Good luck finding the cause!
engine, etc.
Note that a fairly common and common cause of these symptoms is considered to be a misfire. The fuel-air mixture in the cylinder does not ignite or the mixture ignites incorrectly, as a result of which the power plant does not produce full power.
The problem does not manifest itself in the same way, since misfires in all cylinders or only in one cylinder may occur sporadically or be present all the time. On some engines, cold misfires disappear after warming up, while on other engines, multiple misfires occur regardless of the temperature of the power unit and its mode of operation.
In this article, we will look at the main causes of misfires in a cylinder, talk about why misfires occur on a cold engine, and how misfires are diagnosed.
Read in this article
What are misfires in cylinders
A misfire is an engine malfunction where the mixture of fuel and air in one or more cylinders does not ignite at the right time, or does not ignite at all.
As a result, the operation of the internal combustion engine is disrupted according to the given cycles, and twitch, power is noticeably lost. Unburned fuel from an idle cylinder enters and burns there. For this reason, misfiring may additionally be accompanied by pops and shots in the muffler.
Let's start with the fact that in the event of problems with the ignition of the mixture on the engine, the main signs are: engine "triple" lumbago in the exhaust system, loss of power, as well as a distinct smell of fuel from the exhaust pipe.
We add that after fixing such gaps by the control unit, the ECU can also forcibly turn off one or even two problematic cylinders. This happens after the control unit analyzes the readings, taking into account the speed of rotation and the cylinders operating at that moment. Measurements are taken every quarter turn (on engines with 4 cylinders).
The misfire counter shuts down idle cylinders after the misfire threshold is exceeded. Shutdown should be understood as the interruption of the fuel supply. Then the cylinder is activated again after a programmed time interval or after the internal combustion engine is restarted.
A similar solution was created in order to protect the catalytic converter in the exhaust system, which is equipped with injection cars. The fact is that the ingress of unburned fuel from idle cylinders destroys the catalyst. The exclusion from the operation of the cylinders in which misfires occurred, allows you to drive on your own to the service station, while the damage to the catalyst will be minimal.
It should be added that even if the problem arose once, that is, it does not have a systematic character, in some cases it is not possible to extinguish a burning check by simple methods (for example, removing the terminal from). In other words, the check is on all the time, but it can only be programmed. At the same time, after connecting the diagnostic equipment to the car, it is possible to detect a misfire in the 2nd cylinder, misfires in the 2nd and 3rd cylinders, etc.
The misfire error itself on the scanner is indicated by the letter "P". For example, p0301 indicates that misfiring in the first cylinder was recorded and recorded in the ECU memory. Error p0302 (misfire in cylinder 2) will indicate exactly the second cylinder, p0300 - random multiple misfires detected, error 300 misfires, excess, etc. In any case, the indicated error indicates the presence of a problem that needs to be fixed.
Misfire: Causes
Having dealt with what misfiring is, it is necessary to identify the reasons why such a failure may occur. The list of possible malfunctions is quite wide, and when a misfire occurs in the cylinders, the diagnosis should take into account the main reasons:
- The composition of the fuel-air mixture, fuel supply. First of all, injection nozzles tend to gradually become clogged with impurities and deposits that are contained in the fuel. As a result, misfiring occurs due to injectors. The injector loses the ability to provide fuel supply in full with respect only to specific modes of operation of the internal combustion engine or constantly. In practice, this is manifested by periodic or constant tripping of the motor under load or at idle, cold and / or after warming up.
- Ignition system, and other elements. It is quite obvious that problems with spark plugs or high voltage wires, as well as the ignition coil and other components, can lead to misfires of the air-fuel mixture in the cylinders.
- or a clear spread of this indicator across the cylinders leads to the fact that the mixture is not compressed enough and ignition problems occur. Low compression may appear as a result of wear,. Also, malfunctions or malfunctions often cause misfiring.
Misfires in the cylinders, sometimes called a "misfire error" are usually easy to notice - the car starts to twitch when accelerating, at idle it "shakes" they also say "motor troubles". The reason is usually related to problems in the ignition or fuel, in especially severe cases, the piston group is to blame. Depending on the severity of the situation, misfiring is accompanied by a loss of engine power.
If misfiring occurs only under certain circumstances, such as under load or in a narrow rev range, then it is difficult to detect them.
For old cars:
On older, carbureted vehicles, the cause will most often be in the ignition system, as they lack many of the complex sensors that can cause misfires. Also, misfire can be caused by a vacuum leak or a bad fuel pump. The first thing to do is determine which cylinder or cylinders are misfiring, and the best way to tell this is the color of the spark plug.
A working plug will have a brownish coloration, while a misfired cylinder plug will be gray or even black.
If the cause is the spark plug, then it must be replaced. The next diagnostic step is to check the ignition wires for wear or damage. If necessary, they must also be replaced.
For most modern cars:
In modern cars, thanks to the OBD-II system, misfiring will always be accompanied by a lit or flashing “Check Engine” signal. 
A flashing "Check Engine" light indicates a more serious misfire problem and should therefore not be driven. The OBD-II diagnostic scanner will show you which cylinder is at fault, but it cannot point to the cause - the injector, spark plug or ignition coil, in the worst case, damage to the piston or cylinder. As with carbureted cars, it's a good idea to take a look at the spark plugs, wires, and ignition coils first. Sometimes, when inspecting the engine in the dark, you can see sparks that come from a “broken” ignition wire.
One way to identify a bad spark plug is to start the car and let it idle. Then sequentially disconnect the ignition wires from the coil or remove the connector from the ignition coils. If, when the engine is turned off, the operation of the engine changes, it starts to twitch more or stall, then the candle or coil is working. Removing the wire from a faulty spark plug or coil - engine operation won't change at all. If a new spark plug in that cylinder doesn't solve the misfire problem, then the coil or wire is at fault. This is how the source of the “motor troit” problem is determined by the elimination method.
If the ignition system is not the source of the misfire problem, then the injector and fuel line need to be checked. A multimeter is used to test the injectors. It measures the resistance of each injector. If the resistance of any of the injectors is outside the specified values, then it must be replaced. You can also check to see if voltage is coming to the injectors. The operation of the injector cannot be evaluated with a multimeter.
Checking the fuel line, pressure in it, compression in the cylinders should be carried out only by a qualified specialist using special equipment.
Common causes of misfires:
- faulty spark plugs or wires
- faulty ignition coil
- worn or damaged piston rings
wear due to fuel - burnt or bent valves
burnt valve - damaged valve springs
- camshaft wear
- inoperative fuel injector
Store currency rubles c.u.
Misfires. Part 1.
MISS
Misfiring is a common drivability problem that can sometimes be difficult to detect and sometimes easy, depending on the cause. The misfire of one of the cylinders of the four-cylinder engine, of course, is impossible not to notice. Losing 25% of engine power is like a horse without one leg. In this case, the engine will shake so hard at idle that it will be given throughout the car. The engine will be difficult to start, and at idle it may even stall, especially if a heavy load goes to auxiliary devices (air conditioning, headlights, rear window electric heater, etc.)
Misfiring increases fuel consumption, degrades vehicle performance, exhaust emissions and idling, and an exhaust gas test will detect unusually high levels of hydrocarbons.
This problem (misfire) can be caused by one of three things: no spark, an unbalanced fuel mixture, or a loss of compression. No spark means that the winding voltage cannot overcome the distance between the electrodes at the end of the spark plug. This could be due to worn, dirty or faulty spark plugs, damaged wires to the spark plugs, or a cracked ignition distributor cap. A weak coil can cause damage to not only one, but all cylinders.
Misfiring can also be caused by a lean fuel mixture (there is not enough gasoline in the fuel mixture to ignite), which in turn can be the result of a clogged or damaged fuel injector, an air leak, or low fuel pressure due to a weak pump, filter, resistance or leaking pressure regulator. Low fuel pressure as well as air leaks often cause damage to all cylinders, not just one of them. A leaking EGR valve (exhaust gas recirculation valve) has the same consequences as an air leak. If one or more misfire codes (P030X) and one EGR system trouble code (P0401) are displayed, then the problem is most likely a carbon buildup under the EGR valve.
Loss of compression means that the fuel mixture is leaking out of the cylinder and not igniting, most likely due to a leaking (burned) exhaust valve or a blown cylinder head gasket. If there is a misfire in two adjacent cylinders, then the gasket between them may have burned out. If the engine is overheating or there is a coolant leak, then the problem may also be in the cylinder head gasket.
Irregular misfires are the hardest to pinpoint, as they may or may not ignite, depending on engine load or operating conditions. Crashes seem to happen for no apparent reason. The engine will sometimes stutter and misfire in cold weather, but as it warms up, it performs better. It can start well and idle, but if you increase the load on it, interruptions in the ignition system begin. Or it works fine most of the time, but occasionally shuts down or starts intermittently for no apparent reason.
DIAGNOSTICS OF MISSES WITH AUTO SCANNER
When the OBD II system detects an abnormal misfire, the "Check Engine" warning light comes on and a DTC (P) is generated corresponding to the misfire in the cylinder. By connecting a conventional autotester or a portable autoscanner (for example, or) to the car's diagnostic connector, you can read the error code. The last digit in the P0300 series code indicates the failed cylinder.
For example, code P0304 indicates that a misfire occurs in the 4th cylinder. The cause may be problems with ignition, compression or fuel. However, code P0204 indicates an injector malfunction (codes of the P0200 series indicate a malfunction in the injector circuit).
If an EGR DTC (for example, P0401) occurs, then the problem is most likely a carbon deposit under the EGR valve.
Codes P0171 or P0174 (lean) may indicate a dirty fuel injector.
If only a misfire code is displayed, check the ignition parts on the correct cylinder. The source of the problem can be a worn or dirty spark plug, a damaged spark plug wire, carbon deposits or moisture inside the ignition coil, or a weak or damaged coil in a multi-coil non-contact ignition system.
Code P0300 stands for Random Misfire, i.e. misfiring is random and occurs in all cylinders. The reason may be a deterioration in the composition of the fuel mixture, for example, significant air leakage, leaking EGR valve or too low fuel pressure (weak pump or faulty pressure regulator).
CAUSES OF PERMANENT MISSES
In the case of persistent misfires during diagnosis, the first step is to isolate the problem cylinder. You can find such a cylinder in the good old way - in turn, disconnect the wires to the spark plugs at idle: if the idle speed does not change, then you have found a faulty cylinder.
You can also check the power balance by cylinder, but this will require wiring diagrams and an engine analyzer. This test is preferable to disconnecting the wires, since the latter will have to deal with voltage that can damage the electronics in the ignition system.
When the wire is physically disconnected from the spark plug, the high voltage spike is not grounded in the usual way through the wire and spark plug, but back through the coil. Most ignition systems can handle these surges intermittently, but not permanently. If the coil or ignition unit is already worn out, this may cause them to fail.
ADVANCED METHOD FOR DIAGNOSTICS OF MISSES WITH A DIGITAL STORAGE OSCILLOSCOPE
An ignition oscilloscope or digital storage oscilloscope will clearly show which cylinder is causing the problem. A construction sample will help determine the ignition voltage in each cylinder. The cylinders will be shown on the display in their ignition sequence from left to right.
A cylinder malfunction is determined if its peak ignition voltage is higher or lower than the peak ignition voltage of other cylinders. Too low ignition voltage will indicate that there is a short to ground. Possible causes include a dirty, faulty, or damaged spark plug, sparking between the spark plug cap and ground, or a shorted wire to the spark plug. Too high ignition voltage means that the spark plug electrode is too wide or very worn, or the wire to the spark plug is open.
If the ignition voltage on all cylinders at idle is about the same, then a test without preparation will help you identify misfires that happen when the engine is under load. To perform this test, open the throttle sharply wide and allow it to close while observing the oscilloscope readings. The ignition voltage should rise on all cylinders, but if one of them has more voltage than the rest, then this is a problem.
A voltage spike above normal indicates high resistance in the high voltage circuit of the ignition system. Check for excessive resistance or broken wire to spark plug. A voltage spike below normal indicates a voltage drop. In this case, look for a dirty, faulty, or damaged spark plug, sparking between the spark plug cap and ground, or a shorted wire to the spark plug. If during the test the ignition misfire is accompanied by low voltage spikes, then the voltage at the coil is weak. This may be due to a damaged ignition coil, but low battery voltage could be an indication of another problem. Check battery and charging voltage.
Then it is worth checking the oscillogram of the primary voltage of the problem cylinder - it will help to draw up a general picture for diagnosis. It will show the start of coil charging, arcing, or the aforementioned peak ignition voltage, spark line and coil oscillation.
The spark burn line is the part of the waveform that comes directly after the ignition voltage spike. By the height of this line, you can find out the composition of the fuel mixture. If the fuel mixture is rich, then the combustion line will be above normal, if the mixture is lean, then the line will be below normal.
A lean mixture in one cylinder can be the result of a leaking intake manifold gasket, air leaking through the injector O-ring, a leaking EGR valve (if located near the cylinder intake port), or a dirty, clogged, or defective fuel injector. Loss of compression due to a leaking (burnt) exhaust valve or a leaky head gasket affects the spark line in the same way.
Note that if the combustion lines for all cylinders are above normal (indicating a lean mixture), the cause may be something that affects the operation of all cylinders: for example, vacuum leak from the intake manifold, vacuum hose leak, recirculation valve leak exhaust, leaking throttle gasket, or low fuel pressure (weak fuel pump or faulty pressure regulator).
A rich fuel mixture in any one cylinder is quite rare, but can occur if a fuel injector is leaking. It is more common to have a rich mixture in all cylinders due to a faulty oxygen sensor, coolant temperature sensor, or a damaged fuel pressure regulator applying too much pressure to the injectors.
You should also pay attention to the "torn" spark line. With a good cylinder, the burn line will be relatively even. On the other hand, a jagged line indicates that a misfire is occurring, possibly due to a lean mixture.
The length of the spark line can tell you what's going on inside the cylinder. If its duration corresponds to more than two milliseconds, then the fuel mixture is too rich for any of the above reasons. If its duration is less than 0/75 milliseconds, the fuel mixture is too lean.
It is also worth checking the fluctuations on the oscillogram. If the coil is good, then the waveform should show at least three or more oscillations after the burn line. If there is less fluctuation, then the coil is faulty.
I would like to note that some professional multi-brand autoscanners have the built-in oscilloscope function - for example.
Among the various breakdowns of a car, you can find such a breakdown as misfiring. If, when starting the car, the engine starts to shake violently, and at idle it stalls altogether, then this is a sign that there is a malfunction. This is especially noticeable when the engine is cold. Multiple misfires are dangerous for the car, as they cause undesirable consequences: increased fuel consumption, increased CO2 emissions, and high engine noise. All this causes unstable operation of the motor of the car. In this article I will talk about what are the causes of misfire and how to repair them.
Misfire errors are indicated as follows:
- P0301 - misfire in 1 cylinder;
- P0302 - in the 2nd cylinder;
- P0303 - misfire in cylinder 3;
- P0304 - misfire in cylinder 4.
This is a phenomenon in a car engine when one of the cylinders is gaining momentum more slowly than the others.
To understand where to start repairs, you need to understand the reasons that provoke multiple misfires.
So let's take a look at them:
- Causes of misfiring in low-quality fuel. If low quality fuel is used, the injectors may become clogged. In this case, the problem can be solved by changing the gas station, or using high-octane gasoline. Also, a pass may appear due to the slightest defects in the fuel pump;
- Due to broken or low-quality candles;
- Causes - damaged high-voltage wires or they have high resistance;
- Ignition and modules are faulty;
- Uneven compression is the source of the cause of abnormal compression of the air-fuel mixture;
- The causes of misfire may be hidden in the gas distribution mechanism. Multiple skipping can occur as a result of improper timing adjustment or when it accidentally fails and wears out. Leaks in hydraulic lifters can also be the cause;
- Failure of one of the cylinders.
By the way, omissions on a cold engine are very noticeable. This behavior of the motor car will not leave the driver indifferent.
Diagnostics and repair
Solving such a problem is easier for those drivers whose car is “charged” with electric brains. At the service station, using a scanner, the car will show what the misfire error is. For example, a misfire in cylinder 4 or a misfire in cylinder 3. What remains to be done by the owners of domestic or inexpensive cars? That's right, a phased check on your own, resorting, so to speak, to the "grandfather method"
To troubleshoot the issue, you can start by doing the following:
- Check wiring. High voltage wires can often be the cause of the problem. It is necessary to carefully check the insulation, all connectors and the fixation of these connectors. On the surface there should be no various chips and cracks. It is also not allowed to bend the core, which often happens with old wiring. In the case when the problem is in the wiring, you will understand it immediately;
- Candles. A thorough check of the candles will help identify the problem, if it is in them. It is necessary to unscrew each candle and make a visual diagnosis of each. They should not have any damage, blockages and the gap should match;
- We look at the distributor. To inspect it, you need to disassemble it. This part is a rather complex mechanism; for disassembly, it is better to use the diagram. The scheme will help to avoid any mistakes during reassembly and save your time;
- Cylinder compensation. You also need to check the compensation in the cylinders. To perform this procedure, you will need some tools: a pressure gauge and a nozzle for the spark plug connector. This nozzle is inserted into the seat of the candle, and the pressure is checked using a pressure gauge;
- Valves. By examining the valves, you can find a malfunction. The fact is that valves can be of poor quality, so they are often the cause. You also need to check the adjustment level. Inspection by the valve is desirable to be carried out only after all the operations indicated above. Valves tend to stray when the car is subjected to strong mechanical shocks. Seals have a very strong effect on compression as a result of their wear;
- View cylinders. To check the cylinder, you need to perform step-by-step checks. Turn the ignition on and set to idle. Next, one by one, start disconnecting the wires from the candles. If at the moment the cable is disconnected, the operation of the motor has changed, then this means that this particular candle is damaged and needs to be replaced.
It is necessary to remember the extremely important thing that this diagnostics and car repair involve contact with high voltage and hot parts. It is necessary not to forget about safety precautions and to work extremely carefully. It is also important, when performing repairs, to follow the sequence indicated above. The sequence will help you identify the problem as quickly as possible.
