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 be intact within the rocker arm assembly. | Replace the valve rocker arms, as required. |
| Worn or bent pushrods | Replace the pushrods. Inspect the top of the pistons for valve contact. If the top of the piston shows valve contact, replace the piston and pin assembly. |
| 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 | Replace the timing chain and sprockets, as required. |
| Worn camshaft lobes | Replace the camshaft and valve lifters. |
| Sticking lifters | Replace, as required. |
| Improper operation of the active fuel management system | Repair, as required. Refer to Cylinder Deactivation (Active Fuel Management) System Diagnosis . |
| Cut or damaged oil pump screen O-ring seal which may cause aeration of the engine oil | Repair, as required. Refer to Oil Pressure Diagnosis and Testing . |
Base Engine Misfire with Abnormal Valve Train Noise
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 lifter leak down rate | Replace the lifters, as required. |
| Worn crankshaft thrust bearing | Check the crankshaft end play. Inspect the thrust bearing and crankshaft. Repair or replace, as required. |
| Damaged or faulty oil filter bypass valve The bypass valve is now internal to the oil filter. | Inspect the oil filter bypass 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. |
| Loose and/or worn valve rocker arm attachments | Inspect the valve rocker arm, bolt, and pedestal. Repair or replace, as required. |
| Worn or damaged valve rocker arm | Inspect the rocker arm for wear or missing needle bearings Replace the valve rocker arms, as required. |
| Bent or damaged push rod | Inspect the following components and replace, as required: The valve rocker arm The valve push rod The valve lifter The valve lifter guide The piston Inspect the top of the pistons for valve contact. If the top of the piston shows valve contact, replace the piston and pin assembly. |
| Improper lubrication to the valve rocker arms | Inspect the following components and repair or replace, as required: The valve rocker arm The valve push rod The valve lifter The oil filter bypass valve The oil pump and pump screen Improper operation of the active fuel management oil pressure relief valve The engine block oil galleries |
| Broken valve spring | Replace the valve spring and spring shim. |
| Worn or dirty valve lifters | Replace the valve lifters. |
| Active fuel management valve lifter with a broken spring | Replace, as required. |
| Stretched or broken timing chain and/or damaged sprocket teeth | Replace the timing chain and sprockets. |
| 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 |
| Cut or damaged oil pump screen O-ring seal which may cause aeration of the engine oil | Repair, as required. Refer to Oil Pressure Diagnosis and Testing . |
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 controls system. Refer to Symptoms - Engine Controls . |
| Loose torque converter bolts | Inspect the torque converter bolts and flex plate. Repair or replace, as required. |
| Loose or damaged flywheel/flex plate | Repair or replace the flywheel/flex plate. |
| 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, pin, and connecting rod. Replace the piston and pin as an assembly, 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. Refer to Piston, Connecting Rod, and Bearing Installation . 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 controls. Refer to Symptoms - Engine Controls . |
| Loose torque converter bolts | Inspect the torque converter bolts and flex plate. Repair, as required. |
| Cracked flex plate - automatic transmission | Inspect the flex plate bolts and flex plate. 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