Abnormalities, such as extreme 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 - Accessory .

Worn, damaged, or mis-aligned accessory drive components or above acceptable 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 incorrectly 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.

An extreme 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.

Inspect the exhaust system for restrictions. Refer to Restricted Exhaust .

Incorrectly installed or damaged vacuum hoses.

Inspect the vacuum hose routing, Refer to Evaporative Emissions Hose Routing Diagram .

Incorrect sealing between the intake manifold and cylinder heads or throttle body.

Replace the intake manifold, gaskets, cylinder heads, and/or throttle body, as required. Refer to Intake Manifold Replacement .

Incorrectly installed or damaged MAP sensor.

The sealing grommet of the MAP sensor should not be torn or damaged.

Repair or replace the MAP sensor, as required. Refer to Manifold Absolute Pressure Sensor Replacement

Worn or loose rocker arms.

The rocker arm bearing end caps and/or needle bearings should be intact and the rocker arm in the correct position.

Replace the valve rocker arms, as required. Refer to Valve Rocker Arm and Push Rod Replacement .

Worn or bent pushrods.

Replace the valve rocker arms, as required. Refer to Valve Rocker Arm and Push Rod Replacement .

Stuck valves.

Carbon buildup on the valve stem can cause the valve not to close correctly.

Repair or replace, as required. Refer to Cylinder Head Disassemble .

A worn or mis-aligned timing chain above acceptable tolerances.

Replace the timing chain and sprockets, as required. Refer to Camshaft Timing Chain and Sprocket Replacement .

Worn camshaft lobes.

Replace the camshaft and valve lifters. Refer to Camshaft Replacement .

Oil pressure above acceptable tolerances.

A lubrication system with oil pressure above acceptable tolerances may lead to above acceptable valve lifter pump-up and loss of compression.

1. Perform an oil pressure test. Refer to Oil Pressure Diagnosis and Testing .
2. Repair or replace the oil pump, as required. Refer to Oil Pump, Screen, and Crankshaft Oil Deflector Replacement .

Failed 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.

Worn piston rings.

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

A damaged crankshaft reluctor wheel.

A damaged crankshaft reluctor wheel can result in different symptoms depending on the severity and location of the damage.

Replace the sensor and/or crankshaft, as required. Refer to Crankshaft and Bearing Removal .

  or 

Crankshaft Position Sensor Replacement .