Automotive Service Excellence (ASE) A8 Engine PerformanceIgnition System Diagnosis and RepairMedium
A technician is inspecting the ignition system of a distributor-equipped vehicle experiencing a rough idle. They find that the distributor cap terminals are heavily corroded. What effect would this corrosion MOST likely have on the ignition system's performance?
- ADecreased primary coil resistance.
- BReduced secondary voltage delivery.
- CAdvanced ignition timing.
- DIncreased dwell angle.
Show answer & explanationAnswer & explanation
Correct answer: B. Reduced secondary voltage delivery.
Corrosion on the distributor cap terminals creates high resistance in the secondary ignition circuit. This high resistance impedes the flow of high voltage from the coil to the spark plugs, resulting in reduced secondary voltage and potentially misfires, especially at idle.
Why the other options are wrong
- A. Corrosion in the secondary circuit would not directly affect primary coil resistance.
- C. Ignition timing is controlled by the PCM/ICM and is not directly affected by corrosion in the distributor cap, although misfires could be a symptom.
- D. Dwell angle is controlled by the primary circuit and the PCM/ICM, and would not be directly increased by corrosion in the secondary circuit.
Distributor Cap Corrosion
Corrosion on distributor cap terminals introduces excessive resistance into the secondary ignition circuit, reducing the high voltage delivered to the spark plugs and causing misfires.
- Increases resistance in secondary circuit.
- Reduces spark plug voltage.
- Causes misfires or rough idle.
Memory trick: Corrosion's grip, the spark can't skip.