What Causes the Loud Engine Noise in a Corolla?
2 Answers
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.
As a mechanic, when I encounter abnormal noises in a Corolla engine, I mainly check these areas: insufficient or degraded engine oil is the most common cause, leading to piston slap due to poor lubrication; the belt system should also be carefully listened to, especially the timing belt tensioner, which can produce a squeaking sound when aged; if accompanied by vibration, it's likely due to damaged engine mounts causing direct contact between the engine and the frame; in older cars with heavy carbon buildup, rapid acceleration can cause knocking sounds; leaking exhaust manifold gaskets produce a puffing sound, a common issue in humid areas. Don’t ignore chain noise during cold starts, as insufficient oil pressure in the VVTi system can wear the guides. If abnormalities are detected, check the trouble codes immediately and note the RPM range where the noise occurs, as this is crucial for diagnosing issues with hydraulic lifters or bearings.
