What Causes High Idle Speed in Small Cars?
3 Answers
High idle speed in small cars is caused by the idle switch not closing, a faulty idle control valve, or intake pipe leakage. Reasons for excessively high idle speed in small cars: Idle switch not closing, faulty idle control valve, intake pipe leakage, incorrect valve timing, fuel injector dripping or clogging, exhaust system blockage, EGR valve opening during idle conditions. Solutions for high idle speed in small cars: Adjust or replace the throttle position sensor, clean or replace the idle control valve, use a diagnostic tool to perform basic idle speed settings. Locate leakage points and reseal or replace relevant components. Check timing marks and readjust valve timing according to standards. Clean and inspect each fuel injector's spray volume to confirm any clogging or leakage. Replace the three-way catalytic converter. Remove carbon deposits from the EGR valve or replace the EGR valve.
My car used to have a severe high idle issue, with the tachometer frequently jumping over 1000 RPM, while the normal range should be around 700-800 RPM. After inspection, it was found that the throttle body had accumulated a lot of carbon deposits, blocking the air intake passage. The engine, not getting enough air, automatically increased the RPM to compensate. Additionally, the air filter hadn't been replaced for a long time, and the excessive dust reduced the intake efficiency. Some vacuum hoses were also aged and leaking, allowing air to mix in and trick the sensors. The most troublesome part was the ECU misjudgment, causing the fuel pump to inject more fuel. All these issues together caused the idle speed to surge, leading to a sharp increase in fuel consumption and exceeding emission standards. For safety, I first tried using throttle body cleaner to spray it down, and if that didn't work, I planned to take it to a professional shop for carbon cleaning and part replacement. Regular maintenance can save a lot of unnecessary expenses. I suggest you also check these areas and address them early to avoid more trouble.
My car's idle speed has suddenly increased, often surging to around 1100 RPM, and I can hear a humming noise when it's quiet. Normally, it doesn't exceed 800 RPM. Recalling that the last maintenance was a year ago, the throttle body might be too dirty and stuck, or the mass airflow sensor might be faulty and inaccurate, causing the ECU to improperly adjust the fuel mixture. Another possibility is that the spark plugs are worn out, leading to poor ignition and unstable engine performance, which forces the RPM to rise. The most noticeable impact is the vibration I feel when the car is parked, and the fuel consumption has increased by almost 20%, costing me a few extra dollars each time I refuel. For a quick self-check: after warming up the engine, I'll remove the air filter to see if it's dirty and inspect the vacuum hoses for cracks. If there's no improvement, I'll need to take it to a technician to read the fault codes with a diagnostic tool. Developing a habit of cleaning the throttle body every six months can prevent this issue.
