Diagnostic Aids
WARNING: This page is about a different car, the 2003 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
The misfire index counts the number of misfires. The scan tool can monitor the misfire index. There is a current misfire counter and a history misfire counter for each cylinder. Use the current misfire counter to determine which cylinder is misfiring. Use the history misfire counter for misfires that are not currently present.
Many different conditions can cause an intermittent misfire. Inspect the following conditions:
- Inspect the Ignition Control (IC) circuit for an intermittent short to ground.
- Check or inspect the fuel for contaminated fuel. See ALCOHOL/CONTAMINANTS-IN-FUEL DIAGNOSIS WITH SPECIAL TOOL or ALCOHOL/CONTAMINANTS-IN-FUEL DIAGNOSIS WITHOUT SPECIAL TOOL . Inspect the fuel filter for a restriction. A restricted fuel filter can cause a misfire.
- Inspect for sticking intake or exhaust valves.
- Inspect the Heated Oxygen Sensor (HO2S) for abnormal voltage readings.
- Inspect for a vacuum leak as a possible cause of the engine misfire.