Base Engine Misfire with Abnormal Valve Train Noise
| Cause | Correction |
|---|
| Worn or loose followers, valve rocker arms The follower, valve rocker arm, roller bearing should be intact and in the proper position. | Replace the followers, valve rocker arms, as required. |
| Stuck valves Carbon buildup on the valve stem can cause the valve not to close properly. | Repair or replace as required. |
| Excessively worn or mis-aligned timing chain or chains | Replace the timing chain or chains and sprockets as required. |
| Worn camshaft lobes | Replace the camshaft or camshafts and SHLAs (valve lifters). |
| Sticking SHLAs (lifters) | Replace the SHLAs as required. |
Engine Noise on Start-Up, but Only Lasting a Few Seconds
| Cause | Correction |
|---|
| Incorrect oil filter without anti-drainback feature | Install the correct oil filter. |
| Incorrect oil viscosity | Drain the engine oil and replace with the correct viscosity oil. |
| High stationary hydraulic lash adjuster (SHLA), valve lifter, leak down rate | Replace the SHLAs, valve lifters, as required. |
| Worn crankshaft thrust bearing | Inspect the thrust bearing and crankshaft. Repair or replace as required. |
| Damaged or faulty oil filter by-pass valve | Inspect the oil filter by-pass valve for proper operation. Repair or replace as required. |
Upper Engine Noise, Regardless of Engine Speed
| Cause | Correction |
|---|
| Low oil pressure | Perform an oil pressure test. Refer to Oil Pressure Diagnosis and Testing . Repair or replace as required. |
| Loose and/or worn follower, valve rocker arm | Inspect the follower, valve rocker arm. Repair or replace as required. |
| Improper lubrication to the followers, valve rocker arms | Inspect the following components, and repair or replace as required: The follower, valve rocker arm The SHLA, valve lifter The oil filter bypass valve The oil pump and pump screen The cylinder head oil galleries The engine block oil galleries |
| Broken valve spring | Replace the valve spring. |
| Worn or dirty stationary hydraulic lash adjusters (SHLAs), valve lifters | Replace the SHLAs, valve lifters. |
| Stretched or broken timing chain or chains and/or damaged sprocket teeth | Replace the timing chain or chains and sprockets. |
| Worn timing chain tensioner or tensioners | Replace the timing chain tensioner or tensioners as required. |
| Worn timing chain shoe or shoes | Replace the timing chain shoe or shoes as required. |
| Worn timing chain guide or guides | Replace the timing chain guide or guides as required. |
| Worn engine camshaft lobes | Inspect the engine camshaft lobes. Replace the camshaft or camshafts and SHLAs, valve lifters, as required. |
| Worn valve guides or valve stems | Inspect the following components, and repair as required: The valves The valve guides |
| Stuck valves Carbon on the valve stem or valve seat may cause the valve to stay open | Inspect the following components, and repair as required: The valves The valve guides |
Lower Engine Noise, Regardless of Engine Speed
| Cause | Correction |
|---|
| Low oil pressure | Perform an oil pressure test. Refer to Oil Pressure Diagnosis and Testing . Repair or replace damaged components as required. |
| 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. |
| Loose or damaged crankshaft balancer | Inspect the crankshaft balancer. Repair or replace as required. |
| Detonation or spark knock | Verify the correct operation of the ignition controls system. Refer to Symptoms - Engine Controls . |
| 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. |
| Damaged oil pan, contacting the oil pump screen An oil pan that has been damaged may improperly position the oil pump screen, preventing proper oil flow to the oil pump. | Inspect the oil pan. Inspect the oil pump screen. Repair or replace as required. |
| Oil pump screen loose, damaged or restricted | Inspect the oil pump screen. Repair or replace as required. |
| 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. |
| 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 crankshaft bearing clearance | Inspect the following components, and repair as required: The crankshaft bearings The crankshaft journals |
| 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. |
Engine Noise Under Load
| Cause | Correction |
|---|
| Low oil pressure | Perform an oil pressure test. Refer to Oil Pressure Diagnosis and Testing . Repair or replace as required. |
| Detonation or spark knock | Verify the correct operation of the ignition controls. Refer to Symptoms - Engine Controls . |
| Loose torque converter bolts | Inspect the torque converter bolts and engine flywheel. Repair as required. |
| Cracked engine flywheel | Inspect the engine flywheel and bolts. Repair as required. |
| Excessive connecting rod bearing clearance | Inspect the following components, and repair as required: The connecting rod bearings The connecting rods The crankshaft |
| Excessive crankshaft bearing clearance | Inspect the following components, and repair as required: The crankshaft bearings The crankshaft journals The cylinder block crankshaft bearing bore |
