What are the causes of poor engine idling?
4 Answers
Poor engine idling is mainly caused by the following reasons: 1. Leakage in the intake system or vacuum system; clogged air filter; malfunctioning idle control valve or auxiliary air valve. 2. Faulty air flow meter; improper idle adjustment; too low fuel pressure. The following are several inspection methods for poor engine idling: 1. First, perform fault self-diagnosis to check if any fault codes appear. 2. Check for leaks in the intake system's pipe joints, vacuum hoses, exhaust gas recirculation system, and fuel vapor recovery system. 3. Check the high-voltage spark; if the spark is too weak, inspect the ignition system.
A few days ago, my car's engine kept shaking at idle and almost stalled, which was really annoying! I looked it up and found it might be due to thick carbon buildup on the spark plugs, which haven't been replaced for a long time, causing poor ignition; or a dirty throttle body affecting smooth air intake. I cleaned the carbon deposits myself with some tools, and the situation improved a lot. If the idle control valve or sensors are faulty, sending incorrect signals to the computer, it can also cause shaking. A leak in the vacuum hose, letting in too much air too quickly, can make the idle unstable. Don’t forget to check the ignition coils and fuel pump—if they’re faulty, the engine won’t get enough power. Regular maintenance, like changing the air filter and oil frequently, can help avoid such issues. For safety, don’t force driving—if the engine stalls while parked, it’s even more dangerous on the highway. In short, fixing it early saves big money.
Last year after buying my car, I noticed the idle speed was always unstable, with the engine sound fluctuating between loud and quiet, which scared me into thinking the fuel quality was poor. Later, the mechanic pointed out the possible causes: the fuel injectors might be clogged, with too much dust causing uneven fuel spray; or the oxygen sensor might be aging, sending inaccurate signals that affect the computer's idle speed adjustment. I learned to check the fuses and battery voltage, as low levels can trigger issues. If the idle problem occurs when the engine is cold, the coolant temperature sensor might be faulty, leading to an improper air-fuel mixture ratio. Don’t overlook oil leaks under the chassis or loose belts, as increased mechanical friction can also burden the engine. It’s recommended to clean the fuel system regularly, use higher-quality fuel additives, and keep the system unobstructed to save money and hassle.
Multiple causes of idle issues: weak ignition due to worn spark plugs; insufficient fuel pressure caused by clogged fuel pump or filter affecting supply; inaccurate air intake from dirty air filters or leaking pipes in the intake system. Faulty sensors like the idle control valve or crankshaft position sensor can mislead the ECU's idle control. Vacuum leaks, such as cracked hoses sucking in extra air, are also culprits. Personal advice: check spark plugs and voltage before DIY fixes, and use a diagnostic tool to read error codes—random adjustments may worsen the problem. Prompt repairs prevent greater damage.
