Circuit/System Testing
- Verify that the following conditions do not exist:
- Vacuum hose splits, kinks, and incorrect connections
- Engine vacuum leaks
- Crankcase ventilation system for vacuum leaks
- Fuel pressure that is too low or too high - Refer to Fuel System Diagnosis .
- Contaminated Fuel - Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
- Exhaust system restrictions
- If you find any of the above conditions, repair as necessary.
- Ignition OFF, remove the T8 ignition coil of the misfiring cylinder, but leave the electrical connector connected.
- Inspect the ignition coil boot for the following conditions:
- Holes
- Tears
- Carbon tracking
- Oil contamination
- water intrusion
- If you find any of the above conditions, repair as necessary.
- Install the J 26792: Spark Tester to the boot of the appropriate T8 ignition coil and ground.
- Attempt to start the engine and observe the J 26792:
Spark Tester. The spark tester should spark.
- If there is no spark, refer to Electronic Ignition System Diagnosis for diagnosis of the ignition coil.
- Ignition OFF, remove the spark plug from the misfiring cylinder. Verify that the spark plug does not exhibit the following conditions:
- Gas, coolant, or oil fouled - Refer to Spark Plug Inspection .
- Cracked, worn, incorrectly gapped - Refer to Ignition System Specifications .
- If there is a condition with the spark plug, replace the spark plug.
- Exchange the suspected spark plug with another cylinder that is operating correctly.
- Engine idling, observe the scan tool Misfire Current Counter parameters. The misfire should not follow the spark plug exchange.
- If the misfire follows the spark plug, replace the spark plug.
- If all conditions test normal, test or inspect for the following:
- A lean or rich Q17 fuel injector - Refer to Fuel Injector Solenoid Coil Test .
- An engine mechanical condition - Refer to SYMPTOMS - ENGINE MECHANICAL .
NOTE:
An erratic or weak spark is considered a no spark condition.