Cause
| Correction
|
| • | Abnormalities, severe cracking, bumps, or missing areas in the accessory drive belt |
| • | Abnormalities in the accessory drive system and/or components may cause engine revolutions per minute (RPM) variations and lead to a misfire diagnostic trouble code (DTC). A misfire code may be present without an actual misfire condition. |
| Replace the drive belt.
|
| • | 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.
|
| • | A 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.
|
| • | 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 sealing between the inlet manifold and cylinder heads or throttle body.
| Replace the inlet manifold, gaskets, cylinder heads, and/or throttle body as required.
|
| • | Improperly installed or damaged manifold absolute pressure (MAP) sensor |
| • | The sealing grommet of the MAP sensor should not be torn or damaged. |
| Repair or replace the MAP sensor as required.
|
Damage to the MAP sensor housing
| Replace the inlet manifold.
|
| • | Worn or loose rocker arms |
| • | The rocker arm bearing end caps and/or needle bearings should be intact and in the proper position. |
| Replace the valve rocker arms as required.
|
| • | 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 tappets.
|
| • | A lubrication system with excessive oil pressure may lead to excessive tappet pump up and loss of compression. |
|
- Perform an oil pressure test. Refer to Oil Pressure Diagnosis and Testing .
- Repair or replace the oil pump as required.
|
| • | 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. |
|
- Inspect for spark plugs saturated by coolant.
- Inspect the cylinder heads, engine block, and/or head gaskets.
- Repair or replace as required.
|
| • | Oil consumption may or may not cause the engine to misfire. |
|
- Inspect the spark plugs for oil deposits.
- Inspect the cylinders for a loss of compression. Refer to Engine Compression Test .
- Perform cylinder leak down and compression testing to identify the cause.
- Repair or replace as required.
|
- A damaged crankshaft reluctor wheel.
- A damaged crankshaft reluctor wheel can result in different symptoms depending on the severity and location of the damage.
| • | Systems with electronic communications, DIS or coil per cylinder, and severe reluctor ring damage may exhibit periodic loss of crankshaft position, stop delivering a signal, and then re-sync the crankshaft position. |
| • | Systems with electronic communication, DIS or coil per cylinder, and slight reluctor ring damage may exhibit no loss of crankshaft position and no misfire may occur. However, a DTC P0300 may be set. |
| • | Systems with mechanical communications, high voltage switch, and severe reluctor ring damage may cause additional pulses and effect fuel and spark delivery to the point of generating a DTC P0300 or P0336. |
| Replace the sensor and/or crankshaft as required.
|
