EZCarFix DIY Auto Repair

Symptom Guide

Engine Idles Too High

Tach sitting high at stoplights? The engine is getting air it shouldn't.

What's happening

The engine idles at 1,200+ RPM instead of settling to 600-800. High idle wastes fuel and makes the car lurch in gear.

How urgent is it? Low — fix at your convenience

Not an emergency, but it stresses the transmission at every stoplight and wastes fuel daily.

Most likely causes

  1. 1

    Vacuum leak

    Unmetered air raises idle; the computer can't pull it back down.

  2. 2

    Faulty idle air control valve

    Stuck open, feeding the engine extra air.

  3. 3

    Dirty throttle body

    Carbon holds the plate open slightly.

  4. 4

    Coolant temp sensor fault

    Computer thinks the engine is cold forever and holds fast idle.

How to diagnose it — in order

  1. 1

    Listen for hissing around the intake (vacuum leak).

  2. 2

    Scan for P0507 idle speed codes.

  3. 3

    Clean the throttle body.

  4. 4

    Check the coolant temp sensor reading against actual engine temp.

Trouble codes tied to this symptom

P0507

If your scanner shows one of these, read its dedicated trouble-code page for the full diagnosis.

Repair guides for this symptom

Repair guide

2015-2022 GMC Canyon SLE - Replace Idle Air Control Valve

Step-by-step DIY for this repair.

Repair guide

2007-2014 Cadillac Escalade - Throttle Body Cleaning

Step-by-step DIY for this repair.

Repair guide

2009-2013 Toyota Corolla - Throttle Body Cleaning Guide

Step-by-step DIY for this repair.

Repair guide

1998-2002 Toyota Corolla — Throttle Body Cleaning DIY Guide | EZ Car Fix

Step-by-step DIY for this repair.

Related symptoms

Rough Idle Engine Stalls / Dies

General diagnostic information, not a factory service procedure. If you're unsure, have a qualified technician confirm the diagnosis before buying parts.