Lower Engine Noise, Regardless of Engine Speed

Cause	Correction
Worn accessory drive components Abnormalities such as severe cracking, bumps or missing areas in the accessory drive belt and/or misalignment of system components.	Inspect the accessory drive system. Repair or replace as required.
Detonation or spark knock	Verify the correct operation of the ignition controls system. Refer to Detonation/Spark Knock in Engine Controls.
Low oil pressure	Perform an oil pressure test. Refer to Oil Pressure Diagnosis and Testing . Repair or replace damaged components as required.
Loose or damaged crankshaft balancer	Inspect the crankshaft balancer. Repair or replace as required.
Loose torque converter bolts	Inspect the torque converter bolts and engine flywheel. Repair or replace as required.
Loose or damaged engine flywheel	Repair or replace the engine flywheel.
Oil pump screen loose, damaged or restricted	Inspect the oil pump screen. Repair or replace as required.
Incorrect piston, piston pin and connecting rod installation Pistons must be installed with the mark or dimple on the top of the piston facing the front of the engine. Piston pins must be centered in the connecting rod pin bore.	Verify the pistons, piston pins and connecting rods are installed correctly. Repair as required.
Excessive crankshaft bearing clearance	Inspect the following components, and repair as required: The crankshaft bearings The crankshaft journals
Excessive connecting rod bearing clearance	Inspect the following components, and repair as required: The connecting rod bearings The connecting rods The crankshaft The crankshaft journals
Excessive piston-to-cylinder bore clearance	Inspect the piston and cylinder bore. Repair as required.
Excessive piston pin-to-bore clearance	Inspect the piston, piston pin, and the connecting rod. Repair or replace as required.