Throttle Position Sensor: Adjustments

IDLE SPEED CONTROL (ISC) SERVO & THROTTLE POSITION SENSOR (TPS)



This adjustment is necessary to provide good driveability and is required after the ISC servo, TPS, mixing body or throttle body have been removed or replaced during routine service.



1. Start and run engine at fast idle to bring coolant to normal operating temperature (185 to 205°F), then turn ignition Off.
2. Disconnect accelerator cable from injector mixer throttle lever.
3. Using suitable digital voltmeter, probe rubber cap side of the TPS connector (leaving connector connected) to make contact with the ``GR'' and ``B'' leads.
4. Turn ignition On and measure TPS output voltage. If voltage is between 200-900 mV, proceed to next step. If voltage is not between 200-900 mV, loosen mounting screws and rotate TPS as necessary to bring voltage within range. Tighten mounting screws and switch ignition Off.
5. Switch ignition On for more than 15 seconds, then switch ignition Off to position ISC servo.
6. Disconnect ISC servo connector, then start engine and set idle speed to 600 RPM with idle speed adjustment screw. Shut engine Off.
7. Using suitable digital voltmeter, probe rubber cap side of the TPS connector (leaving connector connected) to make contact with the ``GR'' and ``B'' leads.
8. Turn ignition On, but do not start engine. Read TPS output voltage. Voltage should be 470 mV. If not, loosen TPS mounting screws and rotate TPS as necessary until output voltage is 470 mV. Apply suitable sealant to TPS mounting screws and tighten.
9. Fully open throttle valve once and let it return to original position. Check TPS output voltage again and correct as necessary.
10. Remove voltmeter, then connect ISC connector.
11. Set idle speed to specifications. Refer to ``Tune Up'' for procedure.
12. Turn ignition switch from Off to On position, then after 15 seconds, return it to the Off position.
13. Connect accelerator cable and adjust as necessary.