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.

1. Inspect the accessory drive components.
2. Repair or replace all damaged components.

Loose and/or damaged crankshaft pulley

A misfire code may be present without an actual misfire condition.

1. Inspect crankshaft pulley and pulley bolt.
2. Repair or replace all damaged components.

Loose and/or damaged flywheel/flex plate

A misfire code may be present without an actual misfire condition.

1. Inspect flywheel/flex plate and flywheel/flex plate attaching bolts.
2. 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 silencers and/or catalytic converters. Repair or replace all damaged components.

Air in fuel system

1. Inspect fuel filter, fuel system for leaks and/or restrictions.
2. Repair or replace all damaged components.

Bent and/or worn valve bridge and finger-follower

1. Inspect valve bridge and valve finger-follower.
2. Repair or replace all damaged components.

Sticking valve

Carbon on the valve stem or valve seat may cause the valve to stick.

1. Inspect valves and valve guides.
2. Repair or replace all damaged components.

Damaged or misaligned timing gears

1. Inspect timing gears.
2. Replace all damaged components.

Worn or faulty camshaft lobes

1. Inspect camshaft lobes.
2. Repair or replace all damaged components.

Excessive piston-to-cylinder bore clearance

1. Perform compression tests.
2. Inspect the piston, piston rings and cylinder bore.
3. 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.)

1. Perform compression tests.
2. Inspect the piston, piston rings and cylinder bore.
3. Repair or replace all damaged components.