What Causes Severe Shaking and Vibration During Cold Idle?
3 Answers
Reasons for severe shaking and vibration during cold idle: 1. Dirty throttle body or excessive carbon buildup in the fuel injectors - it is recommended to clean the throttle body or fuel injectors; 2. Low engine oil temperature and high viscosity, where lubrication for the engine's rotating components has not yet reached the optimal state; 3. Prolonged vehicle use causing the spark plug gap to widen, resulting in reduced ignition energy affecting performance and causing the car to shake - regular cleaning of spark plug carbon deposits and fuel system cleaning are necessary; 4. Faults in the engine management system, such as incorrect coolant temperature or intake air temperature signals, wiring faults, etc., can all cause idle shaking.
I can totally relate to this issue, especially in winter when it's particularly noticeable. When the engine is cold and starts, the idle shakes violently, most likely due to improperly adjusted mixture concentration or unstable cylinder operation. The aging of spark plugs in the ignition system and leakage in high-voltage wires are often overlooked; insufficient ignition energy can cause abnormal operation in a cylinder. Carbon buildup in the throttle body can also lead to miscalculations in air intake, and the ECU compensates by injecting more fuel, which only worsens the shaking. The most frustrating is the aging of engine mount rubber cushions—when the rubber cracks, all the vibrations are transmitted to the car body. Poor oil fluidity slows down oil pressure buildup, and inadequate lubrication can also exacerbate the shaking. I recommend first trying to replace a set of spark plugs and cleaning the throttle body—this should alleviate much of the problem.
My neighbor's old car does the same thing, shaking like a massage chair when cold. Focus on checking three main areas: First, the condition of the ignition system. Are the spark plug gaps too wide? Are there any cracks or electrical leaks in the ignition coils? These can cause misfires and shaking. Second, fuel supply issues. Poor atomization from the fuel injectors or insufficient fuel pressure can lead to a lean air-fuel mixture when cold, causing shaking. Third, the impact of carbon buildup. Carbon deposits in the intake manifold or on the back of the valves can absorb gasoline at low temperatures, disrupting the air-fuel mixture. Another hidden culprit is the engine mounts. When the rubber deteriorates, it loses its cushioning effect, allowing vibrations to transfer directly into the cabin. Don’t rush off after starting in the morning—wait for the RPM to stabilize below 1,000 and see if the shaking lessens.
