**- Bad ignition coil: When a coil overheats, it often stops working until it cools down.
- Bad ICM (Ignition Control Module): The ICM controls the coil and can also cause intermittent spark when it fails.
- Bad pickup coil (in the distributor): The pickup coil signals the ICM when to fire the coil. When it fails, the coil will not fire at the right time, causing intermittent spark.
- Bad crankshaft position sensor: This sensor is used by the ECM to determine when to fire the coil. A faulty sensor can cause intermittent spark.
- Bad wiring: Check all of the wiring involved in the ignition system for damage or loose connections.
- Bad ignition switch: The ignition switch provides power to the coil. A faulty switch can cause intermittent spark.
- Insufficient/faulty grounds: Make sure there is a good ground between the engine and the body.
Troubleshooting steps:
1. Check for spark at the spark plugs while the car is running. If there is no spark, proceed to the next step.
2. Check for spark at the coil. If there is no spark, replace the coil.
3. If there is spark at the coil, check for power at the coil. If there is no power, check the wiring between the coil and the ICM.
4. Check the resistance of the pickup coil. If the resistance is out of spec, replace the pickup coil.
5. Check the resistance of the crankshaft position sensor. If the resistance is out of spec, replace the sensor.
6. Check all of the wiring involved in the ignition system for damage or loose connections.
7. Check the ignition switch for continuity in both ON and OFF positions. Replace if necessary.
8. Check all grounds between the battery, engine, and body. Clean or replace if necessary.
