Symptom guide
Car Idles High
Common causes of idle speed that stays too high after starting or warming up.
Quick answer
High idle often comes from a vacuum leak, dirty or sticking throttle body, idle control issue, throttle sensor fault, or relearn problem after service.
Most likely causes
- Vacuum leak
- Dirty throttle body
- Idle control fault
- Throttle position sensor issue
- Throttle relearn needed
Basic driver checks
- Check whether idle is high only cold or also warm.
- Listen for hissing.
- Scan for P0505, P0507, or throttle codes.
- Review recent battery disconnect or throttle cleaning.
DIY diagnostic path
- Do not adjust sealed throttle stops.
- Inspect intake hoses first.
- Use correct throttle cleaning procedures.
- Perform idle relearn if required by the vehicle.
Common mistakes
- Turning adjustment screws on electronic throttles
- Ignoring vacuum leaks
- Cleaning the throttle body without relearn when required
What to tell the mechanic
Tell the mechanic the warm idle RPM, whether AC changes it, and whether any throttle work was done recently.