Automotive Service Excellence (ASE) A8 Engine PerformanceIgnition System Diagnosis and RepairEasy
During a routine maintenance inspection, a technician notices that the spark plugs from a vehicle with 80,000 miles show signs of significant electrode erosion and a very wide gap. The vehicle owner reports no current driveability issues. What is the most appropriate action for the technician to take?
- ARecommend an engine compression test to check for internal wear.
- BAdvise the customer that no action is needed as there are no current driveability issues.
- CClean the spark plugs and re-gap them to manufacturer specifications.
- DReplace the spark plugs with new ones of the correct type and gap.
Show answer & explanationAnswer & explanation
Correct answer: D. Replace the spark plugs with new ones of the correct type and gap.
Significant electrode erosion and a very wide gap indicate that the spark plugs are worn beyond their service life. While not yet causing driveability issues, they will soon, and replacing them proactively is the correct maintenance action.
Why the other options are wrong
- A. An engine compression test is not relevant to worn spark plugs unless there are other symptoms suggesting internal engine issues.
- B. Ignoring worn spark plugs will inevitably lead to decreased performance and potential misfires in the future.
- C. Severely eroded electrodes cannot be 'cleaned' back to proper function, and re-gapping worn plugs is a temporary fix.
Spark Plug Wear Diagnosis
Assessing the condition of spark plug electrodes and insulators to determine their service life and identify potential engine issues.
- Electrode erosion widens the gap.
- Worn plugs require higher voltage to fire.
- Can lead to misfires and reduced fuel economy.
Memory trick: Look, Measure, Decide: Is the spark plug ready to be retired?