Circuit/System Testing
- Verify that the following conditions do not exist:
- The fuel injector wire harness electrical connectors are connected to the improper fuel injectors. Refer to Engine Controls Schematics .
- Engine 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 .
- Restricted exhaust system-Refer to Restricted Exhaust .
- Ignition OFF, remove the ignition coil from the misfiring cylinder, leaving the electrical connector connected.
- Install the J 26792 to the boot of an ignition coil and ground.
- 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 following conditions do not exist with the spark plug:
- Gas, coolant, or oil fouled
- Cracked, worn, incorrectly gapped-Refer to Spark Plug Inspection .
- If there is a condition with the spark plug, replace the spark plug.
- Exchange the spark plug with another cylinder that is operating correctly.
- Operate the engine under the conditions in which the misfire occurred. This may include putting the engine under a load, turning on the A/C, seat heaters, and rear window defog. 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 Diagnosis (W/CH47976) or Fuel Injector Diagnosis (w/Tech 2) .
- An engine mechanical condition-Refer to Symptoms - Engine Mechanical .
IMPORTANT:
An erratic or weak spark is considered a no spark condition.