What Causes High Idle Speed After Cleaning the Throttle Body?
2 Answers
High idle speed after cleaning the throttle body occurs because the throttle body must be reset after cleaning. If this reset is not performed, the idle speed may fluctuate unpredictably. It is recommended to visit a 4S shop for professional resetting. Below is an extended explanation: Throttle body carbon buildup: During the intake process, impurities can accumulate over time on the throttle plate, leading to increasing carbon deposits. Throttle body movement: The throttle plate encounters resistance during its reciprocating motion. Over time, the engine's computer adjusts the position of the throttle plate, effectively treating the carbon buildup as part of the throttle body. This means the throttle plate does not close completely but stops at the position of the carbon buildup.
After cleaning the throttle body, I encountered an issue with elevated idle speed, primarily because the engine control unit (ECU) needed to relearn the throttle position. The cleaning process removed carbon deposits and altered the airflow path, but the ECU, which had memorized the old parameters, became confused, thinking the throttle was still dirty. As a result, it compensatorily increased the idle speed to maintain stability. It's like how a computer system needs a reboot after an upgrade—you need to drive the car for about 10 to 20 minutes to let the ECU adapt to the new conditions. If the issue persists after driving, you might need to manually reset the ECU. Improper cleaning can also cause air leaks or sensor damage, such as a poorly installed idle air control valve, which allows extra air into the engine and raises the RPM. My advice is not to rush into repairs; observe first. Sometimes, a high-speed drive can resolve the issue. If the problem continues, it's best to have a professional check the voltage and wiring.
