Why is the car's RPM high?

[StGrace]

High engine RPM is generally caused by factors such as poor fuel quality, personal tuning, unclosed idle switch, or exhaust system malfunctions. Below is an analysis of the reasons for high engine RPM: 1. Poor fuel quality: If the fuel added to the vehicle is of low quality, it cannot effectively combine with air for combustion in the engine cylinders, leading to abnormal engine operation, which may result in excessively high RPM. 2. Personal tuning: To prevent manual transmission vehicles from stalling during startup, the RPM can be manually increased. For example, manual transmission models in driving schools often have an RPM 200-300 revolutions per minute higher than personal vehicles. 3. Unclosed idle switch: If the idle switch is not closed, the engine will operate under excessive load, naturally resulting in higher RPM. 4. Exhaust system malfunction: Severe carbon buildup in the vehicle can cause exhaust system malfunctions, leading to insufficient exhaust and consequently higher engine RPM.

[DelBrielle]

A few days ago while getting my car repaired, I came across a vehicle with abnormally high RPMs, most likely due to an issue with the idle control system. When the engine is idling, an abnormal rise in RPM is commonly caused by carbon buildup or sticking in the throttle body, affecting air intake regulation. Another possibility is a faulty accelerator pedal sensor, where the car mistakenly thinks you're pressing the gas pedal and revs up the engine. If the idle air control valve is clogged or malfunctioning, the ECU can't properly regulate it, causing the RPM to fluctuate wildly. If the car also experiences shaking or emits black smoke from the exhaust, it's worth checking the ignition coils or aging spark plugs. It's important to pay attention to the tachometer while driving and clean the throttle body during maintenance. If all else fails, use an OBD scanner to read the error codes. If you notice anything unusual, pull over immediately to inspect—safety first!

[LeLila]

Last time at a red light in neutral, my car's RPM suddenly surged to four or five thousand, making an unbearable roaring noise. Normally, RPM shouldn't be that high, especially when cruising in low gears. Possible causes include a stuck throttle pedal, loose floor mat, or a dirty throttle body affecting idle balance. I also checked online and found that delayed gear shifting in the transmission can also raise RPM. Don't panic if this happens; first, try turning off and restarting the engine to see if it resolves. If not, don't force driving home; take it directly to a trusted repair shop to check the circuits and sensors. Regularly cleaning the air filter can reduce dust entering the intake system, preventing issues proactively.

[VanDaniel]

Having driven for decades, I've seen many cases of high RPM. Abnormally high RPM at idle is mostly caused by ignition system issues, such as carbon buildup on spark plugs causing poor ignition, or a faulty crankshaft position sensor misleading the ECU. RPM not dropping after acceleration? It could be due to worn clutch plates or aged transmission fluid reducing power transfer efficiency. Develop good habits: avoid revving the engine hard during cold starts, change the oil regularly, and check sensors. For a simple fix, buying a bottle of cleaner to spray the throttle body might solve the problem. Early detection and repair save money and hassle.