What are the causes of engine shaking at idle?
3 Answers
The main causes of engine shaking at idle are as follows: 1. Dirty throttle body: Excessive dirt on the throttle valve reduces the intake air volume in the intake manifold. When the air intake fails to meet the normal air-fuel ratio, it causes engine shaking. 2. Excessive carbon deposits inside the engine: Prolonged use of the engine leads to excessive internal carbon buildup, resulting in engine shaking. 3. Faulty spark plugs or ignition coils: Failure to replace spark plugs for an extended period causes excessive electrode gap, affecting ignition timing. This not only causes engine shaking but also increases fuel consumption. 4. Clogged fuel lines or injectors: A dirty fuel filter causes unstable fuel pressure, poor injector atomization, and incomplete combustion. The above conditions will lead to engine shaking.
I've fixed quite a few engine shaking issues, with unstable idling most commonly caused by ignition system problems. Worn spark plugs or leaking ignition coils can make a cylinder misfire, making it feel like the engine is jerking. Carbon buildup in the throttle body blocking the intake passage can also cause shaking, especially noticeable in high-mileage vehicles. Clogged fuel injectors leading to a lean air-fuel mixture is another frequent issue. Also, don't underestimate worn engine mounts - when the rubber cracks, it can't absorb vibrations properly, making the steering wheel shake noticeably. I'd recommend starting with replacing spark plugs and cleaning the throttle body - these two DIY fixes cost just around a hundred bucks.
My neighbor's old Camry had the same issue a few days ago - idling so rough you couldn't even place a teacup steadily. We focused on checking six key areas: 1) Insufficient fuel system pressure due to clogged fuel pump filter causing unstable supply; 2) PCV valve leakage leading to miscalculated air intake; 3) Carbon buildup jamming intake valves from frequent short-distance driving; 4) Intermittent ignition coil failure; 5) Cracked vacuum hose leaks; 6) Poor sensor connector contact. Turned out to be the third issue - carbon-clogged valves. After walnut shell blasting, it became rock steady immediately. Never delay fixing such problems - prolonged vibration severely damages engine mounts.
