Automotive Service Excellence (ASE) A8 Engine PerformanceIgnition System Diagnosis and RepairMedium
A technician is performing an ignition system inspection. They notice that the coil-on-plug (COP) boots on several cylinders show signs of arc tracking (small burn marks or lines). The customer reports occasional misfires during hard acceleration. What is the MOST effective repair strategy for this issue?
- AReplace the affected COP coils and spark plugs.
- BInspect and clean the fuel injectors for the affected cylinders.
- CClean the arc tracking marks with electrical contact cleaner.
- DReplace only the spark plugs on the affected cylinders.
Show answer & explanationAnswer & explanation
Correct answer: A. Replace the affected COP coils and spark plugs.
Arc tracking on COP boots indicates that high voltage is finding an easier path to ground than across the spark plug gap, often due to a breakdown in the boot's insulation or excessive resistance at the plug. To ensure a complete repair, both the damaged COP coil (due to boot damage) and the spark plug (which may have contributed to voltage stress) should be replaced.
Why the other options are wrong
- B. Fuel injector issues are unrelated to arc tracking on COP boots, which is a secondary ignition problem.
- C. Cleaning arc tracking marks is not sufficient; the insulation is compromised, and the problem will recur, especially under load.
- D. Replacing only the spark plugs might temporarily help, but the damaged boot on the COP coil will likely continue to arc, causing future misfires.
Arc Tracking Repair
The repair strategy for ignition components showing arc tracking, which involves replacing both the component with compromised insulation (e.g., COP coil with damaged boot) and the spark plug it serves.
- Arc tracking indicates high voltage leakage.
- Compromised insulation needs replacement.
- Spark plug may be root cause or damaged by arcing.
Memory trick: Arcing means replace both the boot and the spark.