Throttle Body: Testing and Inspection
1987-891. Start engine and allow cooling fan to cycle on and off at least once.
2. Connect suitable timing light, then disconnect and connect coolant thermistor and set basic timing.
3. Stop engine, then connect diagnostic readout box C-4805. Start engine and allow to idle for at least one minute.
4. Using readout box, place read/hold switch in read position and depress ATM button until code 70 appears.
5. Place read/hold switch to hold position, then the following should occur:
a. AIS motor will fully close.
b. Spark stabilization will be inhibited.
c. Idle fuel will become enriched.
d. Engine RPM will be displayed on diagnostic readout box in units of RPM x 10. For example, display 95 equals 95 x 10 which indicates 950 RPM.
6. Check idle RPM. If engine idle speed is within 700-900 rpm on 1987 models or 650-900 rpm on 1988-89 models, then throttle body minimum air flow is satisfactory. If idle RPM is not as specified, replace throttle body.
7. Shut off engine and remove readout box.