Abnormalities, severe cracking, bumps, or missing areas in the accessory drive belt

Abnormalities in the accessory drive system and/or components may cause engine RPM variations and lead to a misfire DTC. A misfire code may be present without an actual misfire condition.

Replace the drive belt. Refer to Drive Belt Replacement .

Worn, damaged, or mis-aligned accessory drive components or excessive pulley runout - May lead to a misfire DTC.

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

Inspect the components and repair or replace, as required.

Loose or improperly installed engine flywheel or crankshaft balancer

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

Repair or replace the flywheel and/or balancer, as required. Refer to Engine Flywheel Replacement or Crankshaft Balancer Replacement .

Restricted exhaust system

A severe restriction in the exhaust flow can cause significant loss of engine performance and may set a DTC. Possible causes of restrictions include collapsed or dented pipes or plugged mufflers and/or catalytic converters.

Repair or replace, as required.

Improperly installed or damaged vacuum hoses

Repair or replace, as required.

Improper operation of the intake rocker arm control system

1. Inspect the intake rocker arm control system for proper operation.
2. Repair, as required.

Improper sealing between the intake manifold, fuel injection manifolds, cylinder heads and throttle body

Replace components, as required.

Improperly installed or damaged MAP sensor and/or seal

The O-ring seal of the MAP sensor should not be torn or damaged.

Repair or replace the MAP sensor, as required.

Improperly installed or damaged EVAP purge solenoid and/or hoses

Repair or replace the EVAP purge solenoid, as required.

Worn or incorrectly adjusted rocker arms

Adjust or replace 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 camshaft timing components

Replace the components, as required.

Worn camshaft lobes

Replace the camshaft, as required.

Faulty cylinder head gaskets and/or cracking or other damage to the cylinder heads and engine block cooling system passages

Refer to Diagnostic Starting Point - Engine Cooling .

Coolant consumption may or may not cause the engine to overheat.

1. Inspect for spark plugs saturated by coolant. Refer to Spark Plug Inspection .
2. Inspect the cylinder heads, engine block, and/or head gaskets.
3. Repair or replace, as required.

Worn piston rings

Oil consumption may or may not cause the engine to misfire.

1. Inspect the spark plugs for oil deposits. Refer to Spark Plug Inspection .
2. Inspect the cylinders for a loss of compression. Refer to Engine Compression Test .
3. Perform cylinder leak down and compression testing to identify the cause.
4. Repair or replace, as required.

Damaged crankshaft sprocket reluctor teeth

Damaged crankshaft sprocket reluctor teeth can result in different symptoms depending on the severity and location of the damage.

Replace or repair, as required.