Idle Speed: Adjustments

Curb idle speed on fuel injected models is controlled by the idle speed control servo and the throttle position sensor. Whenever the ISC servo or the throttle body is removed or replaced, the following adjustment should be performed.

Fig. 5 Adjusting curb idle speed. Fuel injected models:

Fig. 6 Digital voltmeter test connections. 1985-86 models:

Fig. 7 Adjusting throttle position sensor:

Exc. 1987-88 Colt Vista & Conquest
1. Start and run engine at fast idle to bring engine coolant to normal operating temperature (185 to 205°F), then turn ignition Off.
2. Disconnect accelerator cable from injection mixer throttle lever.
3. Loosen throttle position sensor attaching screws, then turn position sensor fully clockwise and tighten attaching screws.
4. Place ISC servo into position by turning ignition switch to On position for approximately 15 seconds, then turning ignition switch Off.
5. Disconnect harness connector at ISC servo, then start engine.
6. Adjust idle speed as shown, Fig. 5, to 600 RPM on 1600cc models or 750 RPM on 2600cc models, then stop engine.
7. On 1985-88 models, while leaving connection intact, probe "GW" and "B" leads of TPS connector, Fig. 6.
8. On all models, turn ignition switch to On position without starting engine, then note throttle position sensor output voltage. Output voltage should be 0.48 ± 0.03 volts. If output voltage is not within specified range, loosen throttle position sensor attaching bolts, then turn throttle position sensor as necessary to obtain specified value, Fig. 7. Apply a suitable sealant to attaching screws, then tighten.
9. Place throttle valve in wide open position, then return it to its original position and check for proper output voltage. Adjust as necessary.
10. Remove adapter (if used) and voltmeter, then (if removed) connect harness connector at ISC servo.
11. Ensure curb idle speed meets specifications, then stop engine.
12. Turn ignition switch to On position, then wait approximately 15 seconds and return ignition to Off position.
13. Connect accelerator cable to injection mixer throttle lever, then adjust accelerator cable.