Misfires: How to Diagnose and Fix the Problem
Car engines are improved every year. However, the problems still remain the same. For example, one of the most common is misfiring. We will tell you what it is, what signs they have. Dealing with an auto mechanic

A person who has been driving for many years cannot imagine his life without a reliable “swallow”. But the car sometimes fails and breaks down. One of the most common problems even in the most modern cars is a misfire. In car repair, it is important to make a correct “diagnosis” in order to know what exactly to repair. Therefore, if it seems to you that your car does not drive well, consumes more gasoline, it is time to pay attention to the problem. We will explain what misfires are, how to recognize them and how to diagnose them.

What is misfire

– First, let’s figure out what ignition is in a car in general. Ignition is the process of igniting the fuel-air mixture in a cylinder, which sets the engine piston in motion. Misfire is a phenomenon in which, for some reason, ignition did not occur, explains auto mechanic Vitaly Churakov.

When skipping, the car starts to “troit” – the motor shakes. Vibration also appears, the car does not develop the necessary power, and at idle the car may stall altogether – for example, when you stop at a traffic light. To avoid bad consequences, you need to determine in time that it is a misfire or other malfunction and fix the problem.

Signs of a misfire

There are several signs by which you can independently identify misfires.

The car accelerates unevenly, gaining speed is difficult for her

This most often indicates that the engine is misfiring. If you notice that your “iron horse” has lost its agility, has become slow, you feel that acceleration and high speeds are difficult for him – this is an occasion to think about whether there are misfires in the engine. The fact is that due to skips, the engine does not work properly, the crankshaft starts to spin at a lower frequency, and because of this, power is lost – everything is interconnected.

Rough idle

The car can stall, the speed floats – then down, then up. For example, this phenomenon can be encountered when you are standing at a traffic light. At idle, the car stalls, and you have to maintain them by lightly pressing the gas pedal. Of course, this is not normal for a car, and first of all it speaks of misfiring.

Vibrations

You may feel the machine vibrate. The fact is, the engine does not work balanced due to one or more idle cylinders. You can feel a strong vibration in the cabin, especially when accelerating or just sitting in a running car.

Zagoranie “waiting” — Check Engine

Almost all modern (and not so) cars are equipped with a check sensor. And when it lights up, motorists start to panic. You should not do this, this sensor, on the contrary, is your assistant. “Check” shows that the motor is running unevenly and gives a signal to the owner of the car. The sensor may come on intermittently to remind the driver that there is some kind of engine error, or stay on if the problem persists and you do nothing to fix it.

Engine sound changes

Each driver knows exactly how his car works, which sound should alert, and which one is considered familiar. Any change in engine sound is a sign that the car needs to be checked. Misfires can make a four-cylinder car engine sound like a three-cylinder.

Also, in addition to changes in the sound of the engine, you may notice lumbago in the exhaust system. Claps appear when the catalytic converter suffers greatly, and it is just malfunctioning due to partial ignition.

All of the above signs indicate that your car is misfiring. In order not to bring the situation to a deplorable one, you should fix the problem as soon as possible and do not drive a faulty car.

Causes of misfiring

There can be a lot of reasons for a misfire – a candle has failed, a malfunction in the air-fuel system, and others. About everything in more detail:

1. Elements of the ignition system are out of order

It can be an armored wire, spark plugs (one of the most common reasons), a coil. For example, the wear of candles leads to the fact that misfires occur precisely at idle, the car will constantly stall. It is better not to waste time and check the spark plugs, a lot depends on them. Look under the hood and check the spark plugs, even if you changed them recently – you could run into a fake or just low-quality / defective spark plugs that simply do not give out a spark.

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2. Malfunction in the fuel-air system

We are talking about nozzles that can be clogged with dirt or other deposits. The engine at idle can “troit” just because of this. The problem goes away after the car warms up. There is no need to close your eyes and rejoice “that it has passed by itself”, the car needs to be checked.

3. Damage inside the engine or low compression

If you’ve checked your injectors and spark plugs and they’re okay, then the car may have low compression or some internal damage. For example, it could be a worn or incorrectly installed timing belt. It just can cause low compression – due to the wrong size of the gaps of the device or leaks in the hydraulic lifters, problems may arise when the mixture ignites.

4. Bad gas

If you get low-quality gasoline, or it leaks, the pressure is low when it is supplied – this can also cause a problem. Check if the pressure regulator in the fuel frame is working properly, if air is leaking or if water is getting into the fuel tank. Many people think why sin on gasoline, because I have always refueled at this gas station, and there have never been any problems. In fact, the fuel batch could have the wrong proportions, respectively, it will not ignite. Poor-quality fuel can also clog nozzles, “kill” candles. Because of it, you can run into expensive repairs, so be careful when changing gas stations and try not to stop at dubious gas stations.

Misfire Diagnosis

If you have at least one of the above signs, check it in more detail. Perhaps the problem lies there.

Diagnostics is carried out in two ways, depending on whether the car is equipped with an ECU (electronic control unit) or not.

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Vehicle with ECU

Troubleshooting in this case is quite simple.

  1. Rent an autotester (engine error reader), find the interpretation of the errors, connect the autotester and wait for the result.
  2. If you have codes P0301, P0302, P0303, P0304, then this indicates that there is a problem in one of the four cylinders, candles or gaskets.
  3. If code P0300 came out, then it is necessary to check the entire system as a whole – this task is already more difficult.
  4. Codes P0201, P0202, P0203, P0204 indicate problems in the injectors, code P0400 indicates a problem in the exhaust manifold.

Vehicle without ECU

This is a harder task. Let’s check the cylinders. Note that not one, but two or three at once may fail, so you will have to check each one manually. To inspect the cylinders and piston rings, you need to remove the valve covers. While you are “climbing” to the cylinders, at the same time check the armored wires, the condition of the candles and the electronics.

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How to fix a misfire problem

Misfiring is not an independent problem, but a consequence of a malfunction. The problem will be found during the diagnostics, and it will need to be fixed. Sometimes it may be enough to replace the candles, but it happens that you have to replace the cylinder block. Note that the diagnosis and repair of misfires is always a contact with high voltage. Observe safety precautions when carrying out such work. If you have no experience in repairing from the word at all or you couldn’t fix the problem yourself, then contact the specialists.

Popular questions and answers

The questions of interest to motorists about the diagnosis of misfires will be answered auto mechanic Vitaly Churakov.

Is it safe to drive with a misfire?
No, it’s not safe. Do not drive a car with a misfire. Firstly, it is not environmentally friendly, secondly, driving can destroy the catalyst, and thirdly, the engine cylinder and pistons wear out. The machine increases consumption, parts wear out. The car will practically not go, it will twitch. Take a taxi or public transport and do auto repair.
What causes misfires?
A misfire does not burn fuel. It enters the combustion chamber and then through the exhaust valve enters the exhaust system. When in the combustion chamber, the fuel directly interacts with the oil and washes it from the cylinder walls, which leads to insufficient lubrication and increased wear of the cylinder and engine piston. If the car is equipped with a catalyst, then unburned fuel getting on the catalyst increases its temperature several times. And this can lead to the destruction of the catalyst. And it’s just not environmentally friendly to “spit gasoline” into the atmosphere.
How does the electronic control unit know about the occurrence of gaps?
The ECU can determine misfires only by indirect signs. For example, by the uniformity of rotation of the crankshaft, determined using the crankshaft position sensor (DPKV). In this case, the cylinder (or cylinders, if there are two or more) in which the misfire occurred is determined mathematically. Another sign can only be determined on cars with individual ignition coils – if a certain coil is out of order, then this indicates 100% that there is a gap in this cylinder.
What is multiple misfires?
This is when the process occurs in several cylinders at once. This situation is more serious than the case when only one cylinder is faulty. It is better to immediately contact the experts. 

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