Component Tests and General Diagnostics

Idle Speed Setting Procedures

TRUCK, UNDER 8500 GVW

2.0L Engine w/Aisan Carburetor and Electronic Idle Speed Control (ISC) - Curb Idle Speed and Fast Idle Speed

Checks/Adjustments

Instructions

1. Idle Speed Verification Procedure
a. Place the transmission in NEUTRAL.
b. Bring engine to normal operating temperature.
c. Turn off all accessories.
d. Verify engine idle speed as specified on the VECI decal. No adjustment required.

2. Closed Throttle Fast Idle rpm/ISC Max Extension Adjustments
a. Turn the ignition key to the OFF position.

Carburetor Fast Idle And Throttle Stop Adjustment:

ISC Motor Connectors:

b. Disconnect ISC DC motor connector. Disconnect the vacuum hose at the fast idle cam breaker (FICB) and plug. Connect insulated jumper clip leads from the battery terminals to the DC motor connector pins. Observe motor shaft movement with battery voltage applied.

CAUTION: Battery voltage must not be applied to the idle tracking switch (ITS) terminals. Isolate the ITS terminals with electrical tape during this test.

c. If the motor extends instead of retracting, reverse polarity across the DC motor connector pins. Disconnect jumper leads after motor has fully retracted.

Carburetor Fast Idle And Throttle Stop Adjustment:

d. Restart engine and check closed throttle rpm (700 or less). If adjustment is required remove tamperproof cap. Adjust throttle stop adjusting screw.
e. Place the fast idle lever on the specified step (1st step) on the fast idle cam.
f. Without touching the accelerator pedal: check/adjust fast idle rpm to specification. Adjust the fast idle adjusting screw.
g. Rev the engine momentarily, allowing engine to return to closed throttle speed.
h. Reconnect jumper leads to ISC motor terminals.
i. If the motor retracts instead of extending, reverse polarity across the DC motor connector pins. Disconnect jumper leads after motor has fully extended.

Carburetor Full Stroke:

j. Check/adjust ISC full stroke speed to 2000 ± 200 rpm. Adjust the full stroke speed adjusting screw.
k. Remove electrical tape from ITS terminals of DC motor connector and reconnect ISC DC motor to engine wiring harness. Remove plug from the FICB vacuum hose and reconnect.

3. Idle Speed Control (ISC) Function Check.

NOTE: If idle speed does not adjust properly in Steps a or d, perform the diagnostic routines.

a. Turn off all accessories. Idle speed should adjust to the speed specified on the VECI decal.
b. Turn ignition switch off.
c. Disconnect engine coolant temperature (ECT) switch.
d. Restart engine. Idle speed should adjust to 1200 ± 75 rpm.
e. Turn ignition switch off, then reconnect ECT switch.

NOTE: After adjustments are completed, reconnect all parts.