What Causes High Idle Speed in Cars?

[LeSadie]

The reasons for high idle speed in cars are: 1. Intake pipe leakage; 2. Faulty idle control valve; 3. Idle switch not closing; 4. Incorrect valve timing; 5. Fuel injector dripping or clogging; 6. Partial blockage in the three-way catalytic converter due to carbon buildup or breakage, increasing exhaust resistance; 7. EGR valve opening during engine idle, allowing exhaust gases to enter the combustion chamber. Solutions for high idle speed: 1. Adjust or replace the throttle position sensor; 2. Clean or replace the idle control valve and use a special decoder for basic idle speed setting; 3. Locate the leakage point, reseal or replace related components; 4. Check timing marks and readjust valve timing according to standards.

[Gloria]

I've been driving for years and have encountered high idle speed several times. It's usually because the throttle body is dirty, with sludge blocking the air intake, causing the engine to automatically increase rpm to compensate. It could also be due to a faulty mass air flow sensor or a vacuum hose leak, which allows excess air to enter and affects idle control. I remember the last time my car's idle speed surged, cleaning the throttle body solved the problem. If not addressed promptly, not only does fuel consumption increase, but engine wear becomes severe, and it may lead to other issues like spark plug carbon buildup. Regular cleaning of these components can prevent problems, especially during frequent stop-and-go driving in the city.

[ODamian]

I just bought a car not long ago, and suddenly the idle speed went up, which made me quite nervous. It's most likely an issue with the idle speed control valve or related sensors, or the circuit connection might be poor, causing the valve to stick. High idle speed not only wastes fuel but also makes the car vibrate more at traffic lights, and if it stalls, it could be troublesome. Once when I went to a repair shop, they checked the air system and computer for me, replaced a small part, and it returned to normal. I suggest not trying to fix it yourself if you notice anything unusual; go straight to a professional to avoid incorrect repairs. Also, pay attention to changes in the tachometer while driving daily. This way, you can drive more at ease and avoid wasting money on repeated fixes.

[EstherLynn]

I found that common causes of high idle speed include throttle body dirt, mass airflow sensor failure, or vacuum line cracks/leaks. The engine requires a stable air-fuel ratio, and abnormalities in these components affect idle. DIY throttle body cleaning can provide short-term improvement, but severe cases require sensor replacement. Regular inspection of line sealing is crucial to avoid trouble after sudden fuel consumption spikes.