What Causes Slight Fluctuation in the Idle Speed Needle?
2 Answers
Reasons for slight fluctuation in the idle speed needle: 1. Idle switch not closing; 2. Faulty idle control valve; 3. Air intake pipe leakage; 4. Fuel injector dripping or clogging; 5. Exhaust system blockage; 6. ECU malfunction; 7. Air filter clogging; 8. Poor cylinder compression. Solutions include: 1. Adjust, repair, or replace the throttle position sensor; 2. Clean or replace the idle control valve and use a dedicated decoder to set the basic idle speed; 3. Locate the leakage point, reseal or replace the component; 4. Clean the fuel injectors, check the fuel injection volume of each injector, and ensure there is no clogging or dripping; 5. Replace the three-way catalytic converter.
I encountered this issue not long ago. At that time, my car's RPM needle kept flickering during idle. After checking for a long time, I found out it was a problem with the ignition system. It could be due to aging spark plugs or poor contact in the ignition coil, causing irregular ignition and making the engine RPM fluctuate. Another common cause is severe carbon buildup, especially around the intake valves, which leads to uneven air intake. A faulty sensor, like the crankshaft position sensor, can also cause the ECU to misjudge the RPM. If left unattended, the engine will shake more and more, fuel consumption will skyrocket, and driving will become uncomfortable and costly. In the end, I went to a professional repair shop to clean the carbon deposits and replace the spark plugs, and now the car runs much smoother.
