Multi-port Fuel Injection (MFI) System Inspection

If components of the multi-port fuel injection (MFI) system (sensors, engine control module, injectors, etc.) are faulty, fuel supply may stop or fuel metering may be incorrect under various engine operating conditions. The following symptoms may occur:

1. Engine does not start or is hard to start.

2. Unstable engine idle.

3. Poor engine driveability.

If any of the above symptoms occur, first perform the normal diagnostic procedure, which includes basic engine checks (ignition system malfunction, incorrect engine adjustments, etc.). Then check the MFI system components using the HI-SCAN (Pro) tester.

• Before removing or installing any component, first read the diagnostic trouble codes, then disconnect the negative battery cable.

• Before disconnecting the battery cables, turn the ignition key to the OFF position. Disconnecting or connecting battery cables with the ignition on or the engine running may damage the engine control module (ECM).

• The control wiring connecting the engine control module to the oxygen sensor is shielded by a ground shield wire, which is connected to the body to eliminate interference from the ignition system and radio. If the shield wire is faulty, replace the control wiring.

• When performing a generator check, do not disconnect the positive (+) battery cable, as this may damage the engine control module.

• Disconnect the battery cables from the vehicle side to prevent damage to the engine control module when charging the battery from an external power source.