Air/Fuel Mixture: Adjustments

Air/fuel mixture is not adjustable.
The following procedure will describe inspection of the mixture ratio feedback system.
1. Start the engine and warm it up until the water temperature indicator points to the middle of the gauge.
2. Operate the engine at 2000 rpm for 2 minutes under no load.

Fig. 54 Inspecting ECU Lamp:

3. Make sure that the L.E.D. on the E.C.U. (located on the floor board in front of the center console) flashes on and off more than 5 times in 10 seconds at 2000 rpm under no load.
a. If OK turn the engine off. The air/fuel mixture feedback system is operating properly. END TEST
b. If not OK, proceed to step 4.
4. Turn the engine off and disconnect the negative battery terminal.
5. Disconnect the harness connector from the ECU.

Fig. 148 O2 Sensor Harness Inspection:

6. Disconnect the O2 sensor connector and use a jumper wire to ground the harness connector to the body or engine (not the sensor wire).
7. With an ohm meter, check for continuity between terminal 19 in the ECU harness and body ground.
a. If OK, proceed to step 8.
b. If not OK, check harness for an open circuit.
8. Reconnect ECU and disconnect the O2 sensor harness jumper wire (do not reconnect the O2 sensor).

Fig. 149 2.5k ohm Resistor:

9. Disconnect engine temperature sensor connector.
10. Install a 2.5k ohm resistor to the harness connector.

Fig. 150 AIV Pipe:

11. Disconnect the AIV delivery tube and plug it off.
12. Reconnect battery ground cable.
13. Start the engine and warm to operating temperature.
14. Check the CO content with an exhaust gas analyzer.
a. If CO is less than 5% at idle, replace the O2 sensor, reconnect the temperature sensor and AIV hose and proceed to step 1.
b. If the CO is more than 5%, proceed to step 15.
15. Turn the engine off and reconnect the AIV tube, O2 sensor and engine temperature sensor.
a. Refer to DIAGNOSIS AND TESTING PROCEDURES and check the fuel pressure regulator.
b. Refer to Computers and Control Systems and check the following components:
^Air flow meter.
^Fuel injector.
^Engine temperature sensor.
^Fuel pressure regulator circuit.