| Condition | Action |
|---|---|
| Abnormalities (severe cracking, bumps or missing areas) in the accessory drive belt. Also worn, damaged, or misaligned accessory drive components or excessive pulley runout. | Abnormalities in the accessory drive belt and/or components may cause engine RPM variations, noises similar to a faulty lower engine and also lead to a misfire condition. A misfire code may be present without an actual misfire condition. Inspect the accessory drive components. Repair or replace all damaged components. |
| Loose and/or damaged crankshaft pulley | A misfire code may be present without an actual misfire condition. Inspect crankshaft pulley and pulley bolt. Repair or replace all damaged components. |
| Loose torque converter bolts | A misfire code may be present without an actual misfire condition. Inspect torque converter bolts and flywheel. Repair or replace all damaged components. |
| Loose and/or damaged flywheel | A misfire code may be present without an actual misfire condition. Inspect flywheel and flywheel attaching bolts. Repair or replace all damaged components. |
| Restricted exhaust system | A severe restriction in the exhaust flow can cause significant loss of engine performance and may set a misfire code. Possible causes of restrictions include collapsed or dented pipes, plugged mufflers and/or catalytic converters. Repair or replace all damaged components. |
| Air in fuel system | Inspect fuel filter, fuel system for leaks and/or restrictions. Repair or replace all damaged components. |
| Bent and/or worn valve bridge and finger-follower | Inspect valve bridge and valve finger-follower. Repair or replace all damaged components. |
| Sticking valve | Carbon on the valve stem or valve seat may cause the valve to stick. Inspect valves and valve guides. Repair or replace all damaged components. |
| Damaged or misaligned timing gears | Inspect timing gears. Replace all damaged components. |
| Worn or faulty camshaft lobes | Inspect camshaft lobes. Repair or replace all damaged components. |
| Excessive piston-to-cylinder bore clearance | Perform compression tests. Inspect the piston, piston rings and cylinder bore. Repair or replace all damaged components. |
| Faulty cylinder head gaskets and/or cracking or other damage to the cylinder heads and engine block cooling system passages. (Coolant consumption may or may not cause the engine to overheat.) | Perform compression tests. Inspect the piston, piston rings and cylinder bore. Repair or replace all damaged components. |
Base Engine Misfire without Internal Engine Noises