Circuit/System Testing

NOTE: You must perform the Circuit/System Verification first.

Verify that the following conditions do not exist:
- Vacuum hose splits, kinks, and incorrect connections
- Engine vacuum leaks
- Crankcase ventilation system vacuum leaks
- Fuel pressure that is too low or too high - Referto Fuel System Diagnosis .
- Contaminated fuel - Referto Alcohol/Contaminants-in-Fuel Diagnosis .
- Restricted exhaust system - Referto Restricted Exhaust .
- If you find any of the above conditions, repair as necessary.
Ignition OFF, remove the T8 ignition coil assembly harness connector and remove the coil assembly.
Inspect the ignition coil spark plug boots for the following conditions:
- Damage
- Carbon tracking
- Oil contamination
- Water intrusion
- If you find any of the above conditions, repair as necessary.
Connect the harness connector to the T8 ignition coil assembly.

NOTE: It may be necessary to secure the J 36012-A to the spark plug boots with electrical tape. See Special Tools .

Install the J 36012-A to the spark plug boots. See Special Tools .
Install the J 26792 between the spark plug boot of the misfiring cylinder and ground. See Special Tools .
Connect the remaining wires to the appropriate cylinders.

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. See Special Tools .
- If there is no spark, refer to Electronic Ignition System Diagnosis .
Ignition OFF, remove the spark plug from the misfiring cylinder. Verify the following conditions do not exist with the spark plug:
- Gas, coolant, or oil fouled - Referto Spark Plug Inspection .
- Cracked, worn, incorrectly gapped - Referto 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.
Ignition ON, engine running, observe the scan tool Misfire Current Counters. 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 - Referto FUEL SYSTEM DIAGNOSIS .
- An engine mechanical condition - Referto Symptoms - Engine Mechanical .