What Causes Sudden Idle Speed Increase That Returns to Normal After Restarting?

[MacAdrian]

The reasons for a sudden increase in idle speed that returns to normal after restarting are: 1. Idle switch not closing; 2. Faulty idle control valve; 3. Intake manifold air leak; 4. Incorrect valve timing; 5. Fuel injector dripping or clogging; 6. Exhaust system blockage; 7. EGR valve opening during idle conditions. Solutions for idle speed increase: 1. Adjust or replace the throttle position sensor; 2. Clean or replace the idle control valve and perform basic idle speed setting with a decoder; 3. Locate the leak, reseal or replace related components; 4. Check timing marks and readjust valve timing according to standards; 5. Clean and inspect each fuel injector's spray volume to confirm any clogging or leakage; 6. Replace the three-way catalytic converter; 7. Remove carbon deposits from the EGR valve or replace the EGR valve.