What Causes Engine Vibration When the AC is On?
2 Answers
Here are the specific reasons for engine vibration when the AC is on: 1. Throttle valve carbon buildup: As a vehicle accumulates mileage, carbon deposits form in various components, particularly the throttle valve. A severely dirty throttle valve obstructs air intake, causing the engine to struggle or barely manage to power the compressor. This results in noticeable vibration when the AC is activated. 2. Damaged engine mounts: The engine naturally vibrates during operation, including when the compressor is engaged, but these vibrations are usually dampened by the engine mounts, making them less noticeable. If the engine mounts collapse or become damaged, the engine's balance is disrupted. Activating the compressor may then reach a resonant frequency, significantly amplifying the vibrations.
Last time my car shook badly when I turned on the AC. After checking at the repair shop for a long time, we found three reasons: First, the engine mounts were worn out. These rubber parts harden and crack over time, causing the engine to shake when suspended. Second, the intake system was too dirty, with the throttle body completely clogged by carbon deposits. Normally, running the AC consumes 10% more power, but with severe carbon buildup, the engine literally struggles to breathe. Third, there was an issue with the spark plugs or ignition coils, especially common in older vehicles. The mechanic said don't underestimate the initial startup of the AC compressor - it can consume an extra 2 horsepower!
