What Causes Intermittent Engine Idle Vibration When the AC is On?
3 Answers
Engine idle intermittent vibration reasons: fuel quality issues, severe engine carbon buildup problems. Specific explanations are as follows: Fuel Quality Issues: The function of fuel is to supply the engine with a certain amount of clean, well-atomized gasoline according to the engine's operating conditions. If there are problems with fuel quality, the quality of the gasoline will deteriorate. Therefore, the engine may experience vibration, which can be resolved by switching to higher-quality fuel. Severe Engine Carbon Buildup Problems: Engine carbon buildup has always been a serious issue. It can be addressed by using higher-quality fuel or purchasing carbon removal products available on the market.
I've been driving for decades and have encountered situations where the engine idles roughly when the air conditioning is turned on. This is usually because the engine is old and can't handle the additional load. When the AC is turned on, the compressor starts, and the engine has to work harder. At idle, the engine is already weak, and the added strain causes it to shake. Worn spark plugs or aging ignition coils could be the culprits—my previous car had this issue due to old spark plugs, and replacing them fixed the problem. It's also worth checking if the air filter is clogged; if it's dirty and restricts airflow, the engine may shake. A weak fuel pump or carbon buildup in the fuel injectors can also cause this. I recommend starting with a simple throttle body cleaning. If it happens frequently, it's best to take it to a repair shop for a thorough inspection to avoid letting a small issue escalate and affect safety.
When I drive my old car, the engine shakes jerkily at idle with the AC on, which is quite annoying. After analysis, the main issue is the sudden increase in engine load. The compressor requires more electricity and power, and since the idle speed is already low, the engine can't keep up, leading to irregularities. Possible causes include insufficient battery charge, a loose belt, or worn engine mounts. I tried replacing the belt, and the shaking reduced slightly. Poor fuel quality can also lead to carbon buildup, clogging the fuel system. In such cases, don't force it; take it to a professional shop for a computer diagnosis of the ignition system or fuel pressure. Regular maintenance, like cleaning the air filter every six months, can help prevent this issue.
