Air/Fuel Mixture: Adjustments

The following procedure will describe inspection and adjustment 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. 55 Inspecting E.C.U. Lamps:

3. Make sure that the green L.E.D. on the E.C.U. (located under the R.F. seat) flashes on and off more than 5 times in 10 seconds at 2000 rpm under no load.
a. If OK proceed to step 4. The O2 sensor is operating properly.
b. If not OK, proceed to step 7.

Fig. 92 Throttle Sensor And Idle Switch:

4. Disconnect the idle switch connector.

Fig. 52 Selecting Modes:

5. Turn the diagnostic mode selector on the E.C.U. fully clockwise and wait for the L.E.D.`s to flash 2 times, then immediately turn the selector counterclockwise. The ECCS system is now in "Mode 2".
6. Race the engine 2 or 3 times, then idle.
7. Make sure that both L.E.D.'s flash more than 9 times in 10 seconds at 2000 rpm under no load.
a. If OK, mixture feedback system (air/fuel mixture) is OK. Reconnect the idle switch connector. Proceed to step 27.
b. If not OK, proceed to step 8.
8. Turning the engine off will return the ECCS system to "Mode 1" (normal operating mode).
9. Turn the engine off and disconnect the negative battery terminal.
10. Disconnect the harness from the ECU.

Fig. 148 O2 Sensor Harness Inspection:

11. Disconnect the O2 sensor connector and use a jumper wire to ground the center terminal in the harness connector to the body or engine (not the sensor wire).
12. With an ohm meter, check for continuity between connector 24 in the ECU harness and body ground.
a. If OK, proceed to step 12.
b. If not OK, check harness for an open circuit.
13. Reconnect ECU (do not reconnect the O2 sensor).

2.5k ohm Resistor:

14. Disconnect the water temperature sensor connector.
15. Install a 2.5k ohm resistor to the harness connector.
16. Reconnect battery ground cable.
17. Start the engine and warm to operating temperature.
18. Check the exhaust CO content with an exhaust gas analyzer.
. a. If the CO is more than 5% at idle, proceed to step 19.
b. If CO is less than 5% at idle, replace the O2 sensor and proceed to step 1.
NOTE: If after replacing the O2 sensor, the system fails the above tests, check the following components. If these components test OK, install a new ECU and retest the system.
Refer to ELECTRICAL COMPONENT TESTING and check the following components:
^Air flow meter.
^Fuel injector.
^Engine temperature sensor.
Refer to FUEL SYSTEMS and check the following component:
^Fuel pressure regulator.
19. Reconnect the O2 sensor and idle switch.
20. Remove the resistor from the temperature sensor connector and reconnect the harness.
21. Turn the engine off and remove the air flow meter.

Air By-Pass Screw:

22. Drill a hole in the air by-pass screw plug of the meter.
WARNING: Do not allow metal shavings to enter the air flow meter.
23. Reinstall the air flow meter.
24. Start the engine and warm to operating temperature.
25. Turn the diagnostic mode selector on the E.C.U. fully clockwise and wait for the L.E.D.`s to flash 2 times, then immediately turn the selector counterclockwise. The ECCS system is now in "Mode 2".
26. Turn the air by-pass screw until both L.E.D.'s flash more than 9 times in 10 seconds at 2000 rpm under no load.
a. If OK, mixture feedback system (air/fuel mixture) is OK.
b. If not OK, replace the air flow meter and proceed to step 1.
27. Turning the engine off will return the ECCS system to "Mode 1" (normal operating mode).