Troubleshooting Problems With Engine Idle
In many ways, engine idle is a good measure of your engine’s health. If anything is going wrong under the hood, there’s a good chance it will be affecting your car’s idle speed and quality. Problems with idle speed, things like slow idle, low idle, bad idle, lumpy idle, fast idle — these are symptoms that should be investigated, troubleshooted, diagnosed and repaired. The following symptoms and related problems should act as a guide in helping you troubleshoot your idle issues.
Symptom: The engine will not idle smoothly, or it stalls during idle when the engine is cold. When the engine is cold and you take your foot off the gas pedal, the engine runs very rough and may even stall. When you run the engine at higher speeds, it seems to run fine.
1. If you have a carburetor, you may have a bad accelerator pump or power circuit.
The Fix: Replace accelerator pump or replace carburetor.
2. There may be a vacuum leak.
The Fix: Check and replace vacuum lines as required.
3. There may be some type of ignition problem.
The Fix: Check and replace distributor cap, rotor, ignition wires and spark plugs.
4. The ignition timing may be set wrong.
The Fix: Adjust ignition timing.
5. There may be a fault in the computerized engine control system.
The Fix: Check engine control systems with a scan tool. Test circuits and repair or replace components as required. (Generally not a DIY job)
6. The EGR valve may be bad.
The Fix: Replace EGR valve.
7. The engine may have mechanical problems.
The Fix: Check compression to determine engine condition.
8. Idle speed set incorrectly.
The Fix: Set idle speed to specs.
9. The fuel injectors may be dirty.
The Fix: Clean or replace fuel injectors.