Idle Speed: Adjustments

Fig. 1 Curb idle speed adjust. 4-97.6 w/740 carburetor.:

Fig. 2 Curb idle speed adjust. 4-97.6 less EFI & W/idle speed control:

4-97.6 LESS EFI

NOTE: Refer to Tune Up Specifications chart for curb and fast idle speeds.

1. Place transmission into Neutral or Park.
2. Start and allow engine to reach normal operating temperature.
3. On models with vacuum operated throttle modulator (VOTM), proceed as follows:
a. Position A/C heat selector in heat and blower switch on high.
b. Disconnect vacuum hose from VOTM, then plug.
c. Install slave vacuum hose from intake manifold vacuum to VOTM.
4. Disconnect and plug vacuum hose from thermactor air control valve bypass.
5. Install a suitable tachometer onto engine as per manufacturer's instructions.
6. On models with VOTM, run engine until cooling fan comes on.
7. On models less VOTM, position fast idle adjustment onto the second highest step of fast idle cam, Fig. 1, then operate engine until cooling fan comes ON.
8. Depress throttle slightly to allow fast idle cam to rotate, then check curb idle speed.
9. On models without idle speed control, proceed as follows:
a. If curb idle speed is not as specified, turn idle speed adjusting screw, Fig. 3, until specified idle speed is obtained.
b. Position transmission into Neutral or Park and recheck curb idle speed.

Fig. 3 Curb Idle speed adjust. 4-97.6 less EFI & idle speed control:

Fig. 4 Curb idle speed adjust W/VOTM:

10. On models with mechanical vacuum idle speed control, proceed as follows:
a. If curb idle speed is not as specified, position transmission into Park and deactivate ISC by disconnecting and plugging ISC vacuum hose.
b. Turn ISC adjusting screw until ISC plunger is clear from throttle lever, Fig. 2.
c. Adjust curb idle speed by turning throttle stop adjusting screw.
11. On models with VOTM, proceed as follows:
a. If VOTM RPM is not as specified, adjust by turning screw on VOTM, Fig. 4.
b. Remove plug and connect vacuum hoses.

Fig. 5 Throttle plate adjust. 4-97.6 & 4-116 W/EFI:

4-97.6 & 4-116 W/EFI

Curb idle speed is adjusted by the EEC IV and the idle speed control (ISC) system. The following procedure is an initial curb idle speed setting with the ISC disconnected. Refer to Tune Up Specifications chart for curb and fast idle speeds.

1. Place transmission into Neutral or Park.
2. Start and allow engine to reach normal operating temperature, then switch ignition OFF.
3. Disconnect and plug both vacuum lines from EGR solenoid.
4. Disconnect power lead electrical connector from ISC.
5. Install a suitable tachometer onto engine as per manufacturer's instructions.
6. Start and operate engine at 2000 RPM for approximately 1 minute. Ensure electric cooling fan comes ON.
7. Apply hand brake.
8. Place transmission into Neutral on manual transaxle models or Drive on automatic transaxle models.
9. Check and if necessary adjust initial curb idle speed within 1-1/2 minutes by turning throttle plate adjusting screw, Fig. 5.