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 (W/O SPECIAL TOOL) and ALCOHOL/CONTAMINANTS-IN-FUEL DIAGNOSIS (W/ SPECIAL TOOL) .
- Exhaust system restrictions
- If you find any of the above conditions, repair as necessary.
- Ignition OFF, remove the 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.
- Remove the fuel pump fuse from the fuse block.
- Install the J 26792 to the boot of the ignition coil and ground.NOTE: An erratic or weak spark is considered a no spark condition.
- Attempt to start the engine and observe the J 26792. The spark tester should spark.
- If there is no spark, refer to ELECTRONIC IGNITION (EI) 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 Misfire Current Counters with a scan tool. 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 fuel injector - Refer to FUEL INJECTOR SOLENOID COIL TEST .
- An engine mechanical condition - Refer to SYMPTOMS - ENGINE MECHANICAL .