See Figures 1, 2, 3, 4, 5, 6, 7 and 8
Before beginning any diagnosis and testing procedures, visually inspect the components of the ignition system and engine control systems. Check for the following:
Check the spark plug wires and boots for signs of poor insulation that could cause crossfiring. Make sure the battery is fully charged and that all accessories are off during diagnosis and testing. Make sure the idle speed is within specification.
You will need a good quality volt-ohmmeter and a spark tester in order to check the ignition system. A spark tester resembles a spark plug without threads and the side electrode removed. Using a modified spark plug is as a spark tester is not recommended.
When attempting to search for ignition troubles, keep in mind the various sensor inputs which the control module uses to calculate timing may affect engine performance. The PCM will alter timing based on sensor inputs as follows:
With this in mind, DETONATION could be caused by low MAP output or high resistance in the coolant sensor circuit. POOR PERFORMANCE could be caused by a high MAP output or low resistance in the coolant sensor circuit.
INPUT VOLTAGE TEST
See Figure 9
- Place the ignition switch in the ON position.
- Using a suitable voltmeter, measure the voltage between the positive (+) terminal of the coil and a ground.
- The standard voltage should be approximately 12 volts. If the voltage is not within specification, check the wiring and connectors. As long as the wiring and connectors are OK, replace the coil if testing deems it to be defective.