Why Does My Car Shake When Idle

If your car vibrates or shakes while sitting still in drive, the engine isn't running smoothly or something is amplifying normal vibration.

Shaking at idle is different from shaking while driving — it's caused by the engine itself rather than wheels or drivetrain. An engine misfire from worn spark plugs, a failing coil pack, or a clogged fuel injector makes the engine run unevenly, which you feel as a shake. Vacuum leaks that lean out the mixture on one bank of cylinders can also cause uneven firing and idle vibration.

Worn or collapsed motor mounts are another major cause of idle shaking. Motor mounts are filled with rubber or hydraulic fluid that absorbs engine vibration. When they wear out, that vibration transfers directly into the cabin. You might notice the shaking is worse in drive than in park because the transmission's torque load shifts the engine against the bad mount. A mechanic can check mounts by putting the car in gear with the brake held and watching for excessive engine movement.

Idle shaking is annoying and usually indicates maintenance that's overdue. Ez Mobile Mechanic checks your spark plugs, coils, vacuum system, and motor mounts at your Jacksonville location. We're a mobile mechanic in Jacksonville who comes to your home, office, or parking lot. No tow truck needed. Call (904) 788-7272 for a diagnosis.