Base Engine Misfire with Abnormal Valve Train Noise
| Cause | Correction |
|---|---|
| Worn or incorrectly adjusted valve rocker arms The valve rocker arm and rocker arm rollers should be intact and in the proper working condition. | Adjust or replace the 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 components | Replace components as required. |
| Worn camshaft lobes | Replace the camshafts as required. |
Base Engine Misfire with Abnormal Valve Train Noise
Engine Noise on Start-Up, but Only Lasting a Few Seconds
| Cause | Correction |
|---|---|
| Incorrect oil filter | Install the correct oil filter. |
| Incorrect viscosity oil | Drain the engine oil and replace with the correct viscosity oil. |
| Worn crankshaft thrust bearings | Inspect the thrust bearings 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. |
Engine Noise on Start-Up, but Only Lasting a Few Seconds
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. |
| Worn camshafts and/or valve rocker arms or improperly adjusted rocker arms | Adjust rocker arms or replace components as required. |
| Improper lubrication to the valve rocker arms | Inspect the following components, and repair or replace as required: The valve rocker arm and shaft The oil filter The oil filter bypass valve The oil pump and pump screen The cylinder head oil galleries The engine block oil galleries and restrictors Inspect the intake rocker arm control system for proper operation. |
| Broken valve spring | Replace the valve spring. |
| Stretched or broken timing components | Replace the timing components. |
| Worn timing belt or tensioner | Replace the timing belt tensioner as required. |
| Worn timing belt | Replace the timing belt as required. |
| Worn camshaft lobes | Inspect the camshaft lobes. Replace the camshafts 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 |
Upper Engine Noise, Regardless of Engine Speed
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 system. Refer to Detonation/Spark Knock in Engine Controls - 3.5L (L66). |
| 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. |
| Cut or damaged oil pump screen O-ring | Replace components 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-pin 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 arrow on the top of the piston facing the front of the engine. | Verify the pistons, piston pins and connecting rods are installed correctly. Repair as required. |
Lower Engine Noise, Regardless of Engine Speed
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 system. Refer to Detonation/Spark Knock in Engine Controls - 3.5L (L66). |
| 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 |
Engine Noise Under Load