Uneven engine operation at low revs – what can it mean?

Every driver knows that uneven operation of the car engine at idle does not mean anything good. It can appear not only during high frost or high humidity, but also at very high temperatures. Ignoring this warning signal can end really badly and mean an expensive repair. What can uneven operation of the engine at idle indicate?

When we leave the car at idle, that is, at idle speed (the so-called loose), and do not press the accelerator, his engine should work evenly and steadily. At this time a constant dose of fuel reaches the engine, which ensures optimal operation of all components. How to recognize that something is wrong? You will notice it on the tachometer, which will begin to move rapidly, a more trained ear can hear it without too much trouble, in addition, the vehicle will also feel vibration

What should you check first?


As we mentioned, at idle a constant dose of fuel reaches the engine, so that it should work steadily. If this is not the case, you should first check the fuel and air filters. When they are dirty, not only will the engine run unevenly, but it can also result in a big problem with getting the required crankshaft speed.

Flow meter and fuel pump

The flow meter is responsible for air flow, if it has been damaged or is dirty, wrong information will be transmitted to the control system, resulting in the controller miscalculating the fuel dose to ensure proper engine operation

Problems with the fuel pump are more serious faults that result in similar consequences as a faulty air mass sensor. Its destruction or contamination cause that to the engine does not get the optimal dose of fuel, so it works unevenly even without adding gas

Spark plugs

One of the most common causes of uneven operation of the engine at slow speeds are spark plugs. They can be damaged or incorrectly mounted. In this case it will be necessary to find defective or not screwed plugs or replacement of all without exception, which is associated with a higher cost of repair. In newer car models however we recommend a visit to the garage, where a mechanic will safely carry out the exchange. Then we can be sure that no damage has been done to any electronic components that are located near the spark plugs

Lambda sensor

This element checks the quality of car exhaust gases for air content. In doing so, it examines whether the fuel mixture is rich or poor. Its main task is to ensure that the exhaust fumes coming out of our car are the least harmful to the environment. A malfunction caused by a dirty or damaged lambda probe also affects the rough running of the engine.

Depending on the type of engine and the fuel it is powered by, the malfunctions may vary. When you notice that your car’s engine is running unevenly, it’s worth checking the above elements yourself or visit a mechanic who will thoroughly check the fuel system for leaks or necessary repairs. While at first uneven operation does not cause much danger and affects mainly the comfort of driving, neglect and ignoring the symptoms can lead to a serious and costly engine failure.

Main photo: christian buehner/

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