Why Does the Car Shake at Idle Speed?
3 Answers
Reasons why the car shakes at idle speed: 1. The throttle is dirty or the fuel injector has excessive carbon deposits. 2. Issues with the ignition system. At this time, it is necessary to check the working condition of the spark plugs, high-voltage wires, and ignition coils. Poor performance of the ignition system or bad spark plug firing can also cause such faults. 3. Unstable oil pressure. If you have already cleaned the engine carbon deposits, cleaned the throttle, replaced the oil pads and spark plugs, but still find the car shaking at idle speed, it is recommended to go to a 4S shop to check whether the fuel supply pressure and the intake pressure sensor are normal. 4. Aging of the engine mounts.
My car used to shake like a massage chair at idle, and later I found out it was caused by carbon buildup. A dirty throttle body can make the air intake unstable, and worn spark plugs can also lead to uneven ignition—these are the most common issues. Also, worn engine mounts can cause shaking; that rubber vibration damper gets stiff over time and can't handle the vibrations. Last time, I had a fuel delivery problem—clogged fuel injectors or a faulty fuel pump can make the engine shake like it's gasping for air. These issues are actually quite easy to diagnose: just go to the shop, read the trouble codes, and let the mechanic check the carbon buildup in the cylinders with a borescope, and you can usually pinpoint the problem.
I've encountered idle vibration issues several times, and the most easily overlooked cause is engine mounts. When the rubber deteriorates, it's like springs losing elasticity - engine vibrations transmit directly into the cabin. Additionally, worn-out spark plugs with insufficient ignition energy or faulty ignition coils can cause shaking. I remember one instance where a loose fuel cap caused vacuum leakage, making my teacup dance on the dashboard during idle. Regular throttle body cleaning is crucial - excessive carbon buildup disrupts air intake accuracy and easily causes vibration. Pay special attention to cold start shaking, which might indicate faulty coolant temperature sensors causing incorrect air-fuel mixture.
