What Are the Causes of High Car Idle Speed?
2 Answers
The causes of high car idle speed include: 1. Throttle sticking or not closing properly; 2. Additional air valve failure; 3. Idle speed control valve failure; 4. Water temperature sensor failure; 5. Air conditioning switch or power steering pressure switch failure; 6. Crankcase forced ventilation valve failure; 7. Intake system air leakage; 8. Generator charging voltage too low. The solutions for high car idle speed are: 1. Check the operating sound of the idle speed control valve. If there is no sound, it indicates a fault in the idle speed control valve; 2. Locate the leakage point and reseal or replace the relevant components; 3. Measure the fuel injection volume of the injector. If the fuel injection volume exceeds the standard, the injector may be dripping.
I've been running an auto repair shop for over a decade, and high idle speed issues pop up all the time. The most common culprit is carbon buildup in the throttle body - when sludge gets stuck in those tiny gaps, it allows uneven air intake, making the ECU compensate by injecting more fuel. Sometimes it's a cracked intake pipe leaking air, especially when rubber hoses age and develop splits. Faulty sensors can also be to blame; a bad coolant temperature sensor might make the engine think it's still cold, causing it to rev unnecessarily when it's actually warmed up. Sticking idle control valves are another frequent offender - they get jammed halfway when they should return to position. I advise car owners to regularly clean their throttle bodies and monitor cold-start RPM fluctuations. If you notice your tachometer won't settle at stoplights, get it fixed early to save on fuel costs.
