Base Engine Misfire with Abnormal Valve Train Noise
| Cause | Correction |
|---|
| Worn or loose rocker arms The rocker arm bearing end caps and/or needle bearings should intact within the rocker arm assembly. | Replace the valve rocker arms as required. |
| Stuck valves Carbon buildup on the valve stem can cause the valve to not close properly. | Repair or replace as required. |
| Excessively worn or mis-aligned timing chain | Replace the timing chain and sprockets as required. |
| Worn camshaft lobes | Replace the camshaft and valve lash adjusters. |
| Sticking lifters | Replace 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 oil. Install the correct viscosity oil. |
| High valve lash adjuster leak down rate | Replace the lash adjusters 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. |
| Malfunctioning camshaft position actuators - improper oil viscosity or contamination. The result is camshaft actuator locking pin does not lock | Verify correct engine oil viscosity by changing the engine oil and filter. Reevaluate the concern. Isolate the noise to a specific camshaft position actuator. Replace the camshaft actuator, oil and filter. |
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 valve rocker arm attachments | Inspect the valve rocker arm stud, nut or bolt. Repair or replace as required. |
| Worn valve rocker arm | Replace the valve rocker arm. |
| Improper lubrication to the valve rocker arms | Inspect the following components, and repair or replace as required: The valve rocker arm The valve lifter The oil filter bypass valve The oil pump and pump screen The engine block oil galleries |
| Broken valve spring | Replace the valve spring. |
| Worn or dirty valve lifters | Replace the valve lifters. |
| Stretched or broken timing chain and/or damaged sprocket teeth | Replace the timing chain and sprockets. |
| Worn, damaged, or faulty timing chain tensioners | Replace tensioners |
| Worn engine camshaft lobes | Inspect the engine camshaft lobes. Replace the camshaft and 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 system. Refer to Symptoms - Engine Controls . |
| Loose torque converter bolts | Inspect the torque converter bolts and flywheel. Repair or replace as required. |
| Loose or damaged flywheel | Repair or replace the 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. Refer to Symptoms - Engine Controls . |
| Loose torque converter bolts | Inspect the torque converter bolts and flywheel. Repair as required. |
| Cracked flywheel, automatic transmission | Inspect the flywheel bolts and flywheel. 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 |
