ISC Motor and TPS - Adjustment
NO: STB-83-14-009DATE: December, 1983
MODEL: 1984 Turbo Cordia/Tredia: 1984 Starion
SUBJECT:
ISC/TPS ADJUSTMENT
DESCRIPTION
1984 Starion and turbocharged 1984 Cordia/Tredia models have a new idle Speed Control (ISC) servo motor which performs the functions of opening the throttle during cranking, fast idle speed control, A/C idle-up control and throttle modulation on deceleration. The ISC servo motor adjusts throttle position very precisely by means of a motor-driven screw acting upon a lever on the throttle shaft.
Also connected to the throttle shaft is the Throttle Position Sensor (TPS), which senses throttle position and sends an appropriate voltage signal to the ECI computer. (The TPS was used on the 1983 Starion.)
Since both the ISC and TPS are connected to the same shaft (See Figure 1), a change in the adjustment of one affects the adjustment of the other. Therefore, It is important always to observe this precaution:
PRECAUTION:
WHENEVER THE ISC SERVO MOTOR IS ADJUSTED OR REMOVED AND INSTALLED, THE TPS MUST ALWAYS BE CHECKED AND ADJUSTED.
1. With the engine at operating temperature, all lights and accessories OFF and the transmission in NEUTRAL, turn the ignition switch ON (do not start engine) and leave it ON for a full 15 seconds.
NOTE:
This sets the ISC servo motor to the specified position.
2. Loosen the two screws retaining the TPS; twist the TPS fully clockwise, and temporarily tighten the screws. See Figure 1.
3. With the ignition switch OFF, disconnect the ISC connector (see Figure 2) and then start the engine.
Table 1: IDLE RPM SPECIFICATIONS FOR TPS/ISC SETTING
4. After the engine has idled 30 seconds, adjust idle speed to specifications in table I using the Idle Speed Adjusting screw shown in Figure 3.
5. Turn off the ignition and reconnect the ISC connector.
6. Insert the negative(-) probe of a digital voltmeter into the green/ black wire of the TPS connector and the positive (+) probe into the green/white wire. See Figure 4.
NOTE:
Do not disconnect the connector.
7. Turn the ignition switch ON (do not start the engine) and read TPS output voltage.
TABLE II:
TPS OUTPUT VOLTAGE SPECIFICATIONS
8. Adjust the TPS by loosening the retaining screws and rotating the TPS until the specified voltmeter reading in Table II is obtained. Tighten the screws.
9. Fully open the throttle once, then return it to its original position and check again for output voltage. Readjust if necessary.
10. Remove the voltmeter.
11. Make sure curb idle is at specification:
SERVICE MANUAL UPDATE
The new voltage specification for Cordia/Tredia Turbo in Table II has been adopted to help maintain a more accurate engine RPM when returning to Idle. Please place the orange label on page 14-16 of the 1984 Cordia/Tredia Service Manual as a reference to this bulletin.