ASE Ignition Systems 2 — Questions and Answers
Question 1: What typically causes carbon tracking on a spark plug boot or ignition coil tower?
- Excessive fuel pressure forcing deposits upward
- High humidity causing moisture on the coil surface
- Compromised insulation allowing voltage to arc along the surface to ground (Correct answer)
- Low engine oil causing heat damage
Correct answer: Compromised insulation allowing voltage to arc along the surface to ground
Carbon tracking results from high-voltage arcing along the surface of degraded insulation, depositing conductive carbon that creates a permanent low-resistance path causing misfires.
Question 2: What is the primary function of the ignition control module (ICM)?
- Regulate alternator charging voltage
- Switch primary coil current on and off to induce secondary high voltage (Correct answer)
- Control fuel injector timing and duration
- Regulate idle speed via the IAC motor
Correct answer: Switch primary coil current on and off to induce secondary high voltage
The ICM switches the primary coil circuit on and off based on PCM signals; when primary current is interrupted, the collapsing magnetic field induces high voltage in the secondary winding.
Question 3: Which spark plug electrode material offers the longest service life in modern vehicles?
- Copper core
- Nickel alloy
- Platinum or iridium (Correct answer)
- Zinc alloy
Correct answer: Platinum or iridium
Platinum and iridium have extremely high melting points and corrosion resistance, allowing extended service intervals of up to 60,000–100,000 miles.
Question 4: Abnormally high secondary ignition circuit resistance most commonly indicates what condition?
- Retarded ignition timing
- Worn spark plug electrodes, a wide plug gap, or damaged spark plug wires (Correct answer)
- Low battery voltage during cranking
- A faulty crankshaft position sensor
Correct answer: Worn spark plug electrodes, a wide plug gap, or damaged spark plug wires
High secondary resistance is most often caused by worn plug electrodes with increased gaps, carbon/oil fouling, or deteriorated high-voltage spark plug wires.
Question 5: In a distributor-less ignition (DIS) system, what does the camshaft position sensor determine?
- Fuel injector pulse width for sequential injection
- Which cylinder is on its compression stroke to fire the correct coil (Correct answer)
- Engine coolant temperature for timing correction
- Throttle opening rate for spark advance
Correct answer: Which cylinder is on its compression stroke to fire the correct coil
The camshaft position sensor provides cylinder identification — telling the PCM which cylinder is approaching TDC on compression so the correct coil is fired.
Question 6: Engine knock (detonation) is most often caused by which ignition-related condition?
- Over-retarded ignition timing
- Excessively advanced ignition timing (Correct answer)
- A weak ignition coil producing low voltage
- Incorrect spark plug wire routing
Correct answer: Excessively advanced ignition timing
Over-advanced timing fires the mixture too early, causing combustion pressure to peak before TDC and creating the pressure spikes heard as knock or detonation.
Question 7: What is the typical recommended replacement interval for iridium spark plugs?
- 15,000–30,000 miles
- 30,000–45,000 miles
- 60,000–100,000 miles (Correct answer)
- 150,000–200,000 miles
Correct answer: 60,000–100,000 miles
Iridium spark plugs are rated for 60,000 to 100,000 miles due to iridium's extreme hardness and high melting point, which dramatically slows electrode erosion.
ASE Ignition Systems 2
What typically causes carbon tracking on a spark plug boot or ignition coil tower?