Rough Idle
The problem
Rough idle — shaking, uneven RPM, or stalling at stoplights — usually means the engine isn't burning fuel evenly at low speed. It may feel fine on the highway, which makes it easy to postpone — but misfires waste fuel and can damage the catalytic converter.
Symptoms
- Visible vibration 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 opposite)
- Rough after filling with gas
Can I keep driving with a rough idle?
Mild roughness with no warning lights — schedule diagnosis soon; avoid extended idling.
Active misfire (flashing check engine light or severe shake) — drive gently to a shop or stop if it worsens under load.
Stalling in traffic is a safety issue — don't defer.
Common causes
- Ignition misfire — plugs, coils, wires
- Vacuum leak or unmetered air
- Dirty throttle body or idle air control issue
- Fuel trim problems — injector, regulator, or sensor
- Engine mount worn (shake at idle, less under load)
What happens next at LugsNPlugs Automotive?
- 1. Note cold vs. hot behavior and any recent fuel or service work.
- 2. We review live fuel trim and misfire counters — not just stored codes.
- 3. We prioritize fixes that restore smooth idle and protect emissions components.
Colorado Springs independent repair — dealer-level diagnostics, not a call center. Browse all common problems