What it usually is
- Worn spark plugs or failing coilmost common
Misfire codes, worse under load.
Fix: Tune-Up & Spark Plug Replacement → - Vacuum leakcommon
Lean codes P0171/P0174, hissing under the hood, high idle.
Fix: Check Engine Light Diagnostics → - Dirty throttle body or idle controlcommon
Stalls at stops, idle hunts.
Fix: Tune-Up & Spark Plug Replacement → - Clogged or leaking injectorcommon
Misfire that moves between cylinders, fuel smell.
Fix: Fuel Injector Service & Replacement → - Failed engine mountless common
Vibration you feel but the engine is actually running fine.
Fix: Engine & Transmission Mount Replacement →
What to do right now
- Note whether it's worse cold or hot, in gear or in Park.
- Check for a check engine light.
- Book a diagnostic — a scan with live data usually pins it.
How a mobile mechanic handles it
We come to where the car is — that's the whole point when it's a rough idle situation. We diagnose with a professional scan tool and proper testing, tell you what's wrong and what it costs, and fix it on site when parts allow. Most of these are single-visit repairs in your driveway.
FAQ
Common questions
Will a fuel additive fix rough idle?
Only if the cause is mildly dirty injectors. It won't fix a coil, plug, or vacuum leak.