San Mateo auto repair

A steady, smooth idle feels effortless. When the steering wheel trembles or the seat buzzes at a stoplight, something in the engine or its supports is out of balance. The shake may come and go, get worse with the A/C on, or disappear once the car rolls. Those patterns are helpful clues. Here is what usually causes a rough idle and how it is tracked down. Why Engines Shake at Idle At idle, the engine produces less power and fewer firing events per second, so problems are easier to feel. Any small imbalance, a weak cylinder, a vacuum leak, or a worn mount is not masked by engine speed. The goal is to determine whether the shake originates from an uneven combustion issue within the engine or from a vibration that the mounts can no longer absorb. Misfires and Spark Issues A single cylinder that is not contributing can make the whole engine rock in place. Common reasons include worn spark plugs, failing ignition coils, cracked plug wires on older desig ... read more