What Causes Unstable Idle?

[DelChloe]

Reasons for unstable idle: 1. Idle switch not closing; 2. Faulty idle control valve; 3. Air intake manifold leakage; 4. Incorrect valve timing; 5. Fuel injector dripping or clogging. Troubleshooting methods: 1. Adjust, repair or replace the throttle position sensor; 2. Clean or replace the idle control valve, and use a special decoder to perform basic setting of idle speed; 3. Locate the leakage point, reseal or replace corresponding components; 4. Check timing marks and readjust valve timing according to standards; 5. Clean fuel injectors, inspect each injector's fuel delivery and confirm for any clogging or dripping.