What Causes High Engine RPM but Low Vehicle Speed in an Automatic Transmission?
2 Answers
Automatic transmission vehicles experiencing high engine RPM but low speed is typically caused by transmission failure or engine carbon buildup. Transmission failure: The transmission is a crucial component for changing vehicle speed during driving. Transmission slippage often accompanies severe wear or even burning of clutch or brake friction plates. When the transmission cannot properly adjust vehicle speed, it may result in normal engine rotation without corresponding speed increase when accelerating. Engine carbon buildup: As a vital component for vehicle propulsion, if mixed air or exhaust gases enter the engine interior, it may lead to carbon deposits. This can cause the engine to rotate normally without speed increase when accelerating, affecting normal vehicle operation. Solutions: Check transmission fluid: Inspect the automatic transmission fluid level. If the level is too low or too high, make proper adjustments before verifying whether the transmission still slips. Check cylinder carbon buildup: Prolonged vehicle operation can cause excessive carbon accumulation in cylinders due to continuous operation, affecting normal driving. When encountering this issue, promptly inspect and clean the cylinder carbon deposits.
That time I was driving on the highway, my automatic transmission car's engine RPM suddenly soared to 4000 when I stepped on the gas, but the speed barely moved, stuck around 80 km/h. Panicked, I quickly pulled over to check and found it was a torque converter slipping issue. The torque converter is responsible for transmitting engine power to the transmission. If its clutch plates are worn or there's abnormal oil pressure, the power can't be transferred effectively - just burning fuel without doing any work. This situation is common in older vehicles or those with poor maintenance, like not changing transmission fluid for extended periods where deteriorated fluid reduces friction plate efficiency. I initially thought it was an engine problem, but after taking it to the repair shop, they changed the fluid and test drove it - everything worked normally. So if you encounter high RPM without corresponding speed increase, don't force it - pull over as soon as possible and have professionals inspect it to avoid damaging more components. The repair cost isn't expensive, usually just a few hundred bucks. Remember to check fluid levels every six months as routine maintenance.
