The engine runs intermittently: possible causes and solutions

2024 Author: Erin Ralphs | [email protected]. Last modified: 2024-02-19 11:42

Every car enthusiast has experienced unstable engine operation more than once. This manifests itself in floating speed, both under load and at idle. The motor may run smoothly, and then there is a feeling that it is about to stall. However, it starts working again. What is the reason? Let's try to figure out why the engine is running intermittently, and also learn how to solve this problem.

Cases of unstable operation of internal combustion engines and attempts to eliminate them

During operation, the motor may twitch. Sometimes it's just not possible to drive normally. Automotive service professionals cite various reasons. So, some say that the gasket under the cylinder head is to blame for unstable operation. But the subsequent replacement of it does not give anything. The second diagnostic specialist claims that the valves are to blame. However, after adjusting, there is no result again. The intake specialist saysthat the carburetor / injector is no good and you need to buy a new one or clean it. But, of course, the result is again unsatisfactory.

No matter what they do, the engine runs intermittently. But it turns out that in this case the problem was in the distributor connector - in the chip that is connected to the ignition distributor. Because of this, contact is broken. As you can see, not always unstable work is associated with carburetors, candles and other components. Most of the time it's the wiring. We will elaborate on this.

Reason for unstable operation: ignition system

The first reason is faulty spark plugs. Even if a single candle does not work or does not work correctly, the stable operation of the power unit will not be possible. At least one engine cylinder will malfunction.

This motor operation is due to a faulty ignition coil. This does not happen as often as various candle problems. But the problem should not be ruled out. To understand that something is wrong with the coil, you can by the spark. If its power has noticeably decreased, then as a result this leads to unstable and unstable operation of the internal combustion engine.

Many motorists will be very surprised, but often the engine runs intermittently not at all because of the carburetor or injector - the cause is a beaten or damaged high-voltage spark plug wire. As a result, this leads to a decrease in motor power, its unstable operation and other problems.

Againlet's return to the cover and contacts of the distributor as one of the reasons for the unstable operation of the internal combustion engine. If a contact ignition system is installed in the car, then if the contacts are damaged, the engine may run unevenly. You can forget about any stability "at idle". There are also situations when the ember located in the center of the distributor cover on the inside burns out.

Power system and unstable engine operation

Reliability of the power supply system is a guarantee of smooth and stable operation of the motor. Consider typical malfunctions that cause unstable ICE speeds.

If the engine is running intermittently, the reasons may be low-quality gasoline. Today, at gas stations, such fuel is sold very often. If you fill the car with low-quality fuel, then the engine speed will float, and the car will twitch. Sometimes the car just refuses to go. Experts recommend in this situation to drain all the fuel and check the fuel for the presence of water in it. If the gasoline is drained completely, the entire line is pumped with a pump. Also, it will not be superfluous to flush the carburetor and replace the fuel filters.

Clogged fuel filter or carburetor is another possible cause. Debris in the carburetor can cause the engine to fail to start. If the channels or jets are clogged, then the combustible mixture will not be able to fully enter the combustion chamber. This will instantly affect the operation of the internal combustion engine.

Interruptions in the operation of internal combustion engines and electrical equipment: signs, solutions

If the engine runs rough and it feels likethat the engine is now stalling, you need to pay attention to the tachometer. If at the moment of unstable operation the arrow twitches, then the cause of the malfunction should be sought in the electrical equipment. These are symptoms of short-term failures in the ignition system (no spark). If there is no tachometer, you can determine problems with a spark without it. Vehicle jerks violently while driving.

But it is not always possible to quickly find the causes of a short-term loss of spark. Often, as noted above, these are bad contacts or an ignition coil. Another culprit is the capacitor, contaminated contacts. If new contacts are installed and the motor runs unevenly, then this means that they are bad.

Distributor and capacitor

If the problem is in the capacitor on the distributor (and it can either fail completely or partially), then the motor will start, it can work properly and stably at idle. But in the process of movement, the unit will twitch. This indicates a damaged capacitor. Remove the cover from the distributor, bring the slider so that the contact opens. How is it checked? Hand twist the slider so as to open the contact.

A spark should jump during the opening process. If the capacitor is damaged, it will be blue and strong enough.

Also, there may be insufficient or excessively large gap in the contacts on the distributor. This causes unstable operation of the motor. The stem may wobble from side to side. On himcams and slider installed. Contacts will open without much clarity, which will give interruptions. The stem bushings or the entire distributor should be replaced.

High voltage wires

We have already considered this reason above. If the engine is running intermittently (injector or carburetor, it doesn't matter), then the first thing to pay attention to is the wire connections. If the plug is covered with a green coating, you need to drop oil on it and then wait. Lubricant corrodes oxides and removes them. You can also unscrew and tighten the nuts that secure the wires to the ignition coil.

If this does not help, then by replacing it, you can easily find the failed part. But the difficulty is that if the ignition coil works partially, this can only be detected by replacing it with a known new one.

Intermittent is not tripping

Don't confuse engine misfiring with tripping when one of the cylinders is not functioning. When the motor "troits", there will be no twitches. In this case, bad traction occurs. And at idle, there will still be twitches.

If on a VAZ-2107 car the engine runs intermittently, then the problem is definitely with the ignition system. If, when the gas is pressed sharply, the engine stalls, and then picks up and starts to gain momentum, then the reason is in the carburetor. The ignition system has nothing to do with it. Rarely, dips can be associated with a bad coil. The latter produces a weak spark.

Gasoline pump

It happens that the fuel pump pumps fuel poorly, but there are no failures in quiet mode.

One has only to strongly press the gas, the car will start to twitch, and there will be no strong jerks. The engine will stall and then pick up again. And if you reset the pedal and press it again, the motor will again run smoothly. In this case, it is recommended to replace or repair the fuel pump or its stem. Why does the engine run intermittently? He is running out of gas because the fuel pump is not working efficiently.

Idling and erratic operation

This is also one of the common problems that most car owners face. There are many reasons for this phenomenon. In this case, the malfunctions depend on the type of motor - it is a carburetor unit or an injection unit. Consider each species separately.

Carburetor cars

If the engine idles intermittently, this may indicate that the XX setting in the carburetor has gone astray. It is shifted towards a leaner fuel mixture. In this case, it is recommended to adjust the idle speed to 800-900 rpm on the carburetor.

It is also possible for the solenoid valve to fail. In this case, the engine will work normally only with the choke fully extended. If you remove it, the engine will immediately stall.

Unstable engine operation is also associated with clogged carburetor jets or idle channels. There is not enough air in the fuel here. This problem can be quickly solved by cleaning the carburetor as a whole and the jets.

If there is a suction of excess air, then thisalso leads to a lean mixture. As a result, the engine runs intermittently at idle. Check inlet pipes for leaks.

Injected engine

Modern injection units are more technologically advanced, but there are problems with them. Often a malfunction is associated with a breakdown of a sensor. There are also problems with candles, air supply (here there is a DMRV flow meter on the pipe). The latter can be sucked into the system "from outside".

Also, do not rule out problems with wires. Often the idle sensor or the USR valve fails.

Interruptions on a cold engine

Usually the car will start and immediately stall. Then the next time you turn the key, the engine is already running normally. In the first case, the fuel leaves the fuel pump into the tank, and there is already fuel in the carburetor float chamber. When the key is turned, the engine starts and runs normally, but the pump has not yet sat down to pump gasoline into the carburetor. Because of this, a cold engine runs intermittently.

Also, the carburetor can prepare too lean or too rich a mixture. In injection units, the reason is in the nozzle, which “on a cold” gives the wrong portion of the mixture to any cylinder. The solution to the problem is to clean the stand.

To summarize. As you can see, the motor is unstable for various reasons. First of all, you need to pay attention to the intake and ignition system. Perhaps the problem is inany wiring or sensor.