Rough Idle
A rough idle - shaking, uneven RPM, or stalling at stoplights - usually means the engine is not burning fuel evenly at low speed. It may feel fine on the highway, which makes it easy to put off - but misfires waste fuel and can damage the catalytic converter.
Symptoms
- Shake you feel in the seat or steering wheel at idle
- RPM needle bouncing or dipping toward stall
- Check engine light with misfire codes
- Worse when cold, better when warm - or the other way around
- Rough right after filling with gas
Can I keep driving with a rough idle?
- Mild roughness with no warning lights - schedule diagnosis soon and avoid long idling.
- Active misfire - flashing check engine light or hard shaking - drive gently to the shop or stop if it gets worse under load.
- Stalling in traffic is a safety problem. Do not put it off.
Common causes
- Ignition misfire - spark plugs, coils, or wires
- Vacuum leak - extra air the computer did not meter
- Dirty throttle body or idle air control issue
- Fuel trim problems - injector, regulator, or sensor
- Worn engine mount - shake at idle, less under load
What happens next
- Call us. Tell us cold vs. hot behavior and any recent fuel or service work.
- We review live fuel trim and misfire counters - not just stored codes.
- We find the real problem first. You get a clear estimate before we do any repairs.