If your vehicle is showing rough, shaking, or vibrating idle, here are the most likely causes and the parts you'll need to fix each one.
The rubber dampeners in the mounts degrade, tear, or collapse over time. This transmits normal engine vibrations directly into the cabin, which is highly noticeable at idle but often smooths out when driving.
Worn spark plugs or failing ignition coils cause the engine to skip combustion cycles, creating a stumbling or shaking sensation. This is also a common installation error if a spark plug porcelain is cracked during installation or a coil boot isn't fully seated.
Unmetered air entering the intake manifold throws off the air/fuel mixture, causing a lean condition and rough idle. This frequently happens when a PCV hose or vacuum line is accidentally left disconnected after an air filter change or engine service.
Carbon buildup around the throttle plate or inside the IAC valve restricts airflow when your foot is off the pedal. This starves the engine of air at idle, causing the RPMs to drop too low and the engine to shudder.
A contaminated MAF sensor incorrectly measures incoming air, leading to a poor air/fuel mixture. This is sometimes caused by an installation error where an aftermarket reusable engine air filter is over-oiled, coating the sensor wire.
If a fuel injector is partially clogged or failing electrically, that specific cylinder won't get enough fuel, resulting in a misfire and a shaking engine at low RPMs.
A severe mechanical failure like a burnt exhaust valve, blown head gasket, or worn piston rings causes a permanent loss of cylinder pressure. This results in a constant, heavy misfire that cannot be fixed with tune-up parts.