Partial Combustion (Not Affected By Throttle Position)
- Monitor vehicle's tachometer while cranking engine (at least 250 RPM).
- Check fuel pump operation. See appropriate FUEL PUMP diagnostic chart in SYSTEM/COMP TESTS article. Use DIAGNOSTIC CHARTS DIRECTORY table in SYSTEM/COMP TESTS article to locate chart.
- Perform appropriate INJECTOR MALFUNCTION diagnostic chart in SYSTEM/COMP TESTS article. Use DIAGNOSTIC CHARTS DIRECTORY table in SYSTEM/COMP TESTS article to locate chart.
- Remove vacuum hose from fuel pressure regulator. Apply vacuum and pressure and monitor symptom change.
- Ensure fuel pressure is within specification.
- Ensure ignition timing is within specification.
- Inspect throttle body ports and valves for deposits, wear or plugging. Clean or replace as necessary.
- Check vacuum supply to vacuum hose of fuel pressure regulator. Ensure hose is not plugged. Perform FUEL PRESSURE REGULATOR SOLENOID diagnostic chart (if equipped) in SYSTEM/COMP TESTS article. Use DIAGNOSTIC CHARTS DIRECTORY table in SYSTEM/COMP TESTS article to locate chart.
- Remove vacuum hose from fuel pressure regulator and monitor for symptom change.
- Connect inductive timing light to spark plug wire and check for weakness in flash.
- Ensure spark plug wires are within allowable resistance values.
- Check for spark using spark tester.
- For Starter Signal: Enter self-diagnostic Mode IV and perform appropriate switch tests.
- For Coolant Temp & Crank Angle Sensor: Enter self-diagnostic Mode III and retrieve codes. If vehicle will not start, crank engine before entering self-diagnostic Mode III.
- If Equipped: Perform AIR REGULATOR diagnostic chart in SYSTEM/COMP TESTS article. Use DIAGNOSTIC CHARTS DIRECTORY table in SYSTEM/COMP TESTS article to locate chart.