What Causes Engine Abnormal Noise After Releasing the Throttle?
2 Answers
Possible causes of engine abnormal noise after releasing the throttle: aging or loosening of engine mounts, engine misfire noise, piston slap noise, etc. Aging or loosening of engine mounts: When these engine mounts age or become loose, the engine will vibrate, resulting in abnormal noise; Engine misfire noise: The exhaust gas flow from the vehicle will show obvious intermittency, accompanied by severe shaking of the exhaust pipe, and the abnormal noise from the engine can be clearly heard; Piston slap noise: Due to poor lubrication conditions and excessive wear of pistons and cylinder walls, the clearance tolerance between pistons and cylinder walls exceeds the normal range. During engine operation, the piston skirt impacts the cylinder wall, producing abnormal noise.
I've experienced engine noises after releasing the throttle before, and it really scared me. The most common issue is belt problems, especially when the AC is on. When the tensioner pulley or belt ages, it tends to squeak when you let off the gas. Another possibility is a leaking exhaust pipe gasket—when you suddenly release the throttle, the airflow change can cause a popping sound. In my case, after a lot of troubleshooting, I found that the turbocharger's cooling pipe had come loose, causing metal pieces to vibrate and collide when I let off the gas. Additionally, if the engine mount rubber pads are worn out, the engine can drop slightly when you release the throttle, resulting in a clunking noise. I suggest carefully listening to identify the source of the noise, with special attention to the belt area and the exhaust system under the chassis. If you're unsure, take it to a repair shop ASAP—I ended up spending extra money last time because I waited too long.
