What Causes the Loud Engine Noise in a Corolla?

[LaHarley]

Here are the specific reasons for the loud engine noise in a Corolla: 1. Aging Engine Mounts: The rough operation of the engine can cause aging and abnormal noise in the engine mounts. This noise is caused by overly advanced fuel injection timing and requires readjusting the fuel injection advance angle. 2. Engine Misfire: The engine noise has a certain pattern and is accompanied by unstable engine speed and intermittent black smoke emissions. This uneven noise is caused by diesel leakage from the fuel injector. When this occurs, the fuel injector should be serviced. 3. Piston Slap: During exhaust, the exhaust pipe produces continuous backfire sounds along with black smoke emissions and overheating. Starting the engine becomes difficult, and the backfire sounds lessen at low speeds. This noise is caused by excessively delayed fuel injection timing, and the exhaust pipe position should be adjusted promptly.