Reasons for Unstable Idle Speed in Car Engines?
2 Answers
Reasons for unstable idle speed in car engines are as follows: 1. Faults in the engine air intake supply system: Leakage in the intake manifold or various valves, excessive carbon buildup in the throttle and intake passages, malfunction of idle air actuators, and inaccurate air intake volume. 2. Faults in the engine ignition system: Injector issues, uneven fuel injection or poor atomization by the injectors, leading to an imbalance in power output among cylinders. Common causes include: clogged injectors, poor sealing, fuel spray forming a stream, etc. Fuel pressure faults and inaccurate fuel injection volume. 3. Faults in the car engine fuel system: Issues with the ignition module and ignition coil, spark plugs and high-voltage wires, where faults in spark plugs or high-voltage wires result in reduced spark energy or misfires. Common causes include: incorrect spark plug gap; eroded or damaged spark plug electrodes; carbon buildup on spark plug electrodes; cracked spark plug insulators; excessive resistance in high-voltage wires; leakage in high-voltage wire insulation or plugs; eroded or poorly insulated distributor rotor electrodes. Inaccurate ignition timing, clogged catalytic converters, and faults in automatic transmissions, air conditioning, or power steering that increase idle load can cause unstable idle speed. 4. Faults in the engine electrical circuit.
That day when I was waiting at a red light, the engine was shaking violently with fluctuating RPMs, almost stalling, which scared me so much that I immediately pulled over. Upon checking, I found that the air filter was clogging the intake, preventing proper air mixing; the spark plugs were worn out and failing to ignite; additionally, there was a small hole in the vacuum tube causing air leakage; and the fuel injector was stuck, leading to uneven fuel spray. This kind of unstable idle issue is common in older cars and can easily cause high fuel consumption, exhaust smoke problems, or stalling when stopping, potentially leading to accidents. It's recommended to first clean the air filter and replace the spark plugs; if that doesn't work, then check the vacuum system and fuel lines to ensure safe driving. This experience taught me the importance of timely maintenance, saving trouble down the road.
