Troubleshooting Flow, Strategy and Guidelines

DIAGNOSTIC STRATEGIES

If the MPI system components (sensors, ECU, injector, etc.) fail, interruption or failure to supply the proper amount of fuel for engine operating conditions will result. Therefore, the following situations will be encountered.

1. Engine is hard to start or does not start at all.
2. Unstable idle.
3. Poor driveability.

If any of the above conditions are noted, first check for any ECU diagnostic codes Reading Diagnostic Trouble Codes and then perform basic engine checks (ignition system malfunction, incorrect engine adjustment, etc.), and then inspect the MPI system components with the multi-use tester (MUT) service data test.

NOTE:

1) Before removing or installing any part, read the diagnosis code, then disconnect the battery negative (-) terminal.
2) Before disconnecting the cable from battery terminal, turn the ignition switch to OFF. Removal or replacement of battery cable during engine operation or while the ignition switch is ON could cause damage to the ECU.
3) The harness between the ECU and the oxygen sensor is shielded to prevent the influence of ignition noises and radio interference. When the wire is faulty, the hamess must be replaced.

**TSB # 9113003, DATED FEBRUARY 1991
There are two different wiring harnesses used on this vehicle. A poor connection at a crimp may be causing the check engine light to come on. Refer to the TSB for further information.