Note. All engines use a fixed ignition timing system. Basic ignition timing is not adjustable. All spark advance is determined by the Powertrain Control Module (PCM).
The ignition system used on these engines is referred to as the Direct Ignition System (DIS). The system's three main components are the coils, crankshaft position sensor, and camshaft position sensor. If equipped with the coil on plug ignition system it utilizes an ignition coil for every cylinder, it is mounted directly over the each spark plug.
DESCRIPTION - 5.7L V-8 ENGINE
The ignition system is controlled by the Powertrain Control Module (PCM) on all engines.
Scheme 21
For additional information, also refer to Ignition Coil Description and Operation.
The 5.7L V-8 engine is equipped with 16 spark plugs. Two plugs are used for each cylinder. The 5.7L is also equipped with 8 separate and independent ignition coils. The one-piece coil bolts directly to the cylinder head cover and attaches the coils secondary output terminal directly to a spark plug using a rubber boot seal. Each coil is also equipped with a second output terminal. This second terminal connects a conventional spark plug cable directly to a spark plug on the opposite cylinder bank. A separate primary electrical connector is used for each coil.
Eight conventional spark plug cables are used with the 5.7L. These cables connect a coil on one cylinder bank, directly to a spark plug on the opposite cylinder bank. The cables are placed and routed in a special plastic loom to keep them separated. This loom is clipped to the intake manifold. To prevent a mismatch of cables, a corresponding spark plug / coil number is displayed on each plug cable: 1/6, 2/3, 4/7 and 5/8. These numbers (2) and (3) can also be found on the top of the intake manifold.
Two knock sensors (one for each cylinder bank) are used to help control spark knock.
The 5.7L engine will not use a conventional distributor.
The ignition system consists of
- 16 Spark Plugs (2 per cylinder)
- 8 Separate, Dual-Secondary Output Ignition Coils
- 2 Knock Sensors
- 8 Secondary Ignition Cables
- Powertrain Control Module (PCM)
- Also to be considered part of the ignition system are certain inputs from the Crankshaft Position, Camshaft Position, Throttle Position, MAP and two knock sensors
OPERATION - IGNITION SYSTEM
The crankshaft position sensor and camshaft position sensor are hall effect devices. The camshaft position sensor and crankshaft position sensor generate pulses that are inputs to the PCM. The PCM determines engine position from these sensors. The PCM calculates injector sequence and ignition timing from crankshaft & camshaft position.
DESCRIPTION - PLATINUM PLUGS
The V6 engines use platinum resistor spark plugs. They have resistance values of 6,000 to 20,000 ohms when checked with at least a 1000 volt tester. For spark plug identification and specifications, Refer to SPECIFICATIONS .
Do not use an ohm meter to check the resistance of the spark plugs. This will give an inaccurate reading.
When the spark plugs use a single or double platinum tips and they have a recommended service life of 100,000 miles for normal driving conditions per schedule A in this manual. The spark plugs have a recommended service life of 75,000 miles for severe driving conditions per schedule B in this manual. A thin platinum pad is welded to both or just the center electrode end(s). (Scheme 22) Extreme care must be used to prevent spark plug cross threading, mis-gapping. (Scheme 23)and ceramic insulator damage during plug removal and installation.
Scheme 22
| 1 - APPLY ANTI-SEIZE COMPOUND HERE ONLY |
|---|
| 2 - PLATINUM SPARK SURFACE |
| CAUTION | Cleaning of the platinum plug may damage the platinum tip. |
Scheme 23
| 1 - TAPER GAUGE |
Scheme 24
Always remove the ignition coil assembly by grasping at the spark plug boot, turning the assembly 1/2 turn and pulling straight back in a steady motion.
- Disconnect the negative battery cable.
- Remove the intake manifold. (Refer to appropriate ENGINE article).
- Prior to removing the ignition coils, spray compressed air around the coil area and spark plug or contaminates from spark plug tube. On 3.5L engines, it is necessary to loosen the screws by alternating back and forth. Do not lose the spacers under the coil when loosening the screws.
- Remove the ignitions coil.
- Remove the spark plug using a quality socket with a rubber or foam insert.
- Inspect the spark plug condition.