What Causes Fluctuating Idle Speed After Throttle Body Cleaning?
1 Answers
Possible causes of fluctuating idle speed in a car include: 1. Excessive carbon buildup in the throttle body. 2. Leaks in the intake manifold or various valves. Such faults directly affect the quality of the fuel-air mixture and combustion efficiency. Potential leak points include the intake manifold, vacuum hoses, charcoal canister valve, exhaust gas recirculation (EGR) valve, positive crankcase ventilation (PCV) valve, etc., which require individual inspection. 3. Valve timing faults. Issues like incorrect valve timing, improperly installed timing belt, excessive carbon buildup on intake/exhaust valves, or broken valve springs can cause uneven air intake per cylinder, leading to unstable idle. 4. Clogged catalytic converter. A blocked catalytic converter not only causes idle fluctuation but also results in power loss. 5. Fuel injector malfunction. Problems like poor fuel atomization or clogged injectors may require injector cleaning. 6. Low fuel pressure. Mainly check for clogged fuel filters, fuel pump issues, or deformed fuel lines. 7. Engine misfire. 8. Incorrect ignition timing (too advanced or retarded). Mostly caused by faulty sensors such as MAF sensor, Hall effect sensor, knock sensor, or coolant temperature sensor, requiring diagnostic tool analysis.
