What Causes the Engine to Shake at Idle Every Few Seconds?
3 Answers
Engine shaking at idle every few seconds can be caused by engine misfire, severe carbon buildup in the engine, or aging engine components. Engine Misfire: There are many factors that can cause a misfire. For example, issues with the ignition system—check the condition of the spark plugs, high-voltage wires, and ignition coils. Poor performance of the ignition system or weak spark plug firing can also lead to this type of issue. Severe Carbon Buildup in the Engine: The most common cause of car shaking is a dirty throttle body or excessive carbon deposits in the fuel injectors. When there is too much carbon buildup inside the engine, the fuel sprayed by the cold-start injector can be largely absorbed by the carbon deposits, resulting in an overly lean air-fuel mixture during cold starts. This makes the engine difficult to start, and only when the carbon deposits become saturated with fuel does the engine start more easily. Aging Engine Components: Car shaking can also be related to worn engine mounts. Engine mounts act as the engine's vibration damping system, absorbing minor vibrations during operation. If the engine mounts are faulty, these vibrations can transfer to the steering wheel and the cabin, causing shaking at idle.
My car had a similar issue before, where it would suddenly jerk every few seconds at idle, which was quite annoying. This is most likely related to the ignition system, such as worn-out spark plugs or a faulty ignition coil, causing misfires in one of the cylinders and uneven engine operation. It could also be a fuel system problem, like carbon buildup in the fuel injectors disrupting smooth fuel delivery or a clogged fuel line causing intermittent fuel supply. Another possible cause is an air leak, such as a loose intake pipe allowing extra air to enter, which would upset the air-fuel ratio and cause jerking. I recommend first using an OBD scanner to check for trouble codes. If it shows misfire codes like P0300, focus on inspecting the spark plugs and coils. If you don't have tools, you can try removing the spark plugs yourself to check if the electrodes are eroded or heavily carbon-fouled. For fuel injection issues, adding a bottle of fuel system cleaner might help temporarily. Addressing this early is crucial because prolonged jerking can accelerate engine wear and increase fuel consumption.
As someone who loves tinkering with cars, I always check these points first when encountering idle vibration. The most common issue is with the ignition components—spark plugs can wear out or coils may fail over time, causing misfires and engine shaking due to cylinder imbalance. Next is carbon buildup in the fuel system; clogged fuel injectors disrupt the spray pattern, leading to erratic idle. Air system leaks are also frequent, such as cracked hoses or loose intake ducts, allowing unmetered air to affect the air-fuel mixture. If the engine mounts are worn out, poor damping can make the car shudder. I've found that regular maintenance, like replacing spark plugs and cleaning the throttle body every 20,000 km, works well. When DIY troubleshooting, listen under the hood for irregular misfiring sounds or identify vibration points. Don’t overlook this—worsening vibrations may lead to engine overheating and damage.
