ASE4 Ignition System Diagnosis and Repair 2 — Questions and Answers
Question 1: A spark plug with a white or light gray insulator tip and no deposits indicates:
- Normal combustion
- A lean mixture or overheating condition (Correct answer)
- A rich mixture
- Oil fouling
Correct answer: A lean mixture or overheating condition
A white or very light gray spark plug tip indicates a lean mixture or excessive heat, potentially from an air leak or cooling issue.
Question 2: An ignition coil secondary resistance reads OL (open). This means:
- The coil is within normal range
- The coil secondary winding is open and must be replaced (Correct answer)
- The meter range is set incorrectly
- The coil is shorted
Correct answer: The coil secondary winding is open and must be replaced
An OL (overload/open) reading on secondary resistance means the winding is broken open and the coil cannot produce spark.
Question 3: A COP (coil-on-plug) ignition system has a misfire on cylinder #4. The technician swaps the coil from #4 to #7. If the misfire moves to cylinder #7, this indicates:
- The fuel injector on #4 is faulty
- The coil is the cause of the misfire (Correct answer)
- The spark plug on #4 is fouled
- A compression problem on #4
Correct answer: The coil is the cause of the misfire
A misfire that follows the swapped coil to a new cylinder confirms the coil itself is the source of the fault.
Question 4: Ignition timing that is too far advanced will cause:
- Hard starting and detonation under load (Correct answer)
- Black smoke from the exhaust
- A rich air/fuel mixture
- Low cylinder compression
Correct answer: Hard starting and detonation under load
Over-advanced timing causes the mixture to ignite too early, resulting in engine knock (detonation) and hard starting.
Question 5: A scan tool shows ignition timing retarded by 8° from base timing. This is MOST likely caused by:
- A faulty crankshaft position sensor
- The knock sensor detecting detonation (Correct answer)
- A vacuum leak at the intake manifold
- A failing camshaft position sensor
Correct answer: The knock sensor detecting detonation
The ECM retards timing in response to knock sensor signals to protect the engine from detonation damage.
Question 6: What is the function of the camshaft position sensor in a modern distributorless ignition system?
- It controls the dwell angle of the coil
- It identifies cylinder #1 TDC for sequential fuel and spark delivery (Correct answer)
- It measures camshaft advance angle for VVT control only
- It replaces the crankshaft position sensor if it fails
Correct answer: It identifies cylinder #1 TDC for sequential fuel and spark delivery
The CMP sensor identifies the #1 cylinder at TDC compression so the ECM can sequence coil firing and injector timing correctly.
ASE4 Ignition System Diagnosis and Repair 2
A spark plug with a white or light gray insulator tip and no deposits indicates: