Circuit/System Testing

Verify 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, disconnect the spark plug wire from the misfiring cylinder.
Install the J 26792 Spark Tester between the boot of the spark plug wire and ground.

IMPORTANT: An erratic or weak spark is considered a no spark condition.

Attempt to start the engine and observe the J 26792 Spark Tester. The spark tester should spark.
- If there is no spark, test the spark plug wire for less than 1,000 ohms per 30 cm (per foot). Replace the spark plug wire if more than the specified value. If the spark plug wire test normal, 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 following conditions do not exist with the spark plug:
- Gas, coolant, or oil fouled-Refer to Spark Plug Inspection
- Cracked, worn, incorrectly gapped
- 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 running, disconnect the injector that corresponds to the misfiring cylinder. The engine speed should change.
- If the engine speed changes, replace or re-gap the spark plug.
If all conditions test normal, test or inspect for the following:
- A lean or rich fuel injector-Refer to Fuel Injector Balance Test with Special Tool
- An engine mechanical condition-Refer to Symptoms - Engine Mechanical