Ignition System
4 LessonsFrom spark plugs to coil-on-plug — master ignition diagnosis and repair.
Overview
The ignition system creates the spark that ignites the air-fuel mixture. This module covers ignition coils, spark plugs, triggering mechanisms, ignition timing control, and how the PCM determines the optimal spark event for every combustion cycle.
Key Components
- Ignition coils (COP and coil pack)
- Spark plugs and gaps
- Crankshaft and camshaft position sensors
- Ignition control module/PCM
- Knock sensor
How It Works
The PCM uses crankshaft and camshaft position sensor signals to determine engine position and speed. It calculates the optimal ignition timing based on load, RPM, temperature, and knock sensor input, then triggers the ignition coil to fire the spark plug at precisely the right moment.
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Join the Nation — FreeCommon Problems
- Worn spark plugs causing misfire
- Ignition coil failure (often heat-related)
- Carbon tracking on coil boots
- Crankshaft position sensor failure (no start)
- Knock sensor false readings from carbon buildup
Diagnostic Tips
- Swap coils between cylinders to confirm coil vs. cylinder issue
- Check spark plug condition — it tells a story
- Scope the crank and cam signals for pattern issues
- Misfire counters in Mode $06 show which cylinders are struggling
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