Why does the Chevrolet Epica engine produce abnormal noises?
1 Answers
Most common abnormal noises in the engine depend on the engine's speed state. Many abnormal noises in the engine are clearly related to its load. During diagnosis, the method of gradually removing the load cylinder by cylinder can be used for testing. Typically, the single-cylinder or double-cylinder misfire method is employed to remove the load of one or two cylinders to identify the relationship between the abnormal noise and the load. The specific reasons are as follows: 1. The abnormal noise only exists during idle or low-speed operation. Possible causes include: excessive clearance between the piston and cylinder wall; overly tight piston pin assembly or connecting rod bearing assembly; excessive clearance between the tappet and its guide hole; wear of the camshaft profile; sometimes, a loose starter causing the pulley to make noise (especially noticeable when the speed changes). 2. The abnormal noise occurs when the engine is rapidly accelerated and persists during high-speed operation. Possible causes include: loose connecting rod bearings, melted or improperly sized bearing shells; loose crankshaft bearings or melted bearing shells; broken piston pin; broken crankshaft. 3. When a cylinder misfires, the abnormal noise suddenly disappears or reduces. Possible causes include: piston slap; loose connecting rod bearings; piston ring leakage; broken piston pin. 4. When a cylinder misfires, the noise intensifies, or noise appears where there was none before. Possible causes include: loose piston pin bushing; excessive taper of the piston skirt; piston pin displacement; excessively loose connecting rod bearing cap bolts or melted connecting rod bearing shells; excessively loose flywheel bolts.
