Idle Speed: Adjustments
***UPDATED BY TSB NO. 9001004, JULY 19, 1990Idle speed is programmed into the ECM and controlled through the idle air control (IAC) valve mounted on the throttle body. If the IAC valve is disconnected and reconnected with the engine running, idle speed may be incorrect. Reset IAC valve with the following steps:
1. Depress accelerator pedal slightly, start and run engine for five seconds.
2. Turn ignition "OFF" for 10 seconds.
3. Start engine and check idle speed.
Idle Adjustment Screw:
ALDL Connector:
MINIMUM IDLE SPEED ADJUSTMENT
Minimum idle speed is factory set with a stop screw and sealed. It should only be adjusted when installing a new IAC valve or replacing the throttle body assembly.
1. Check minimum idle speed with engine at normal operating temperature, transmission in "N" or "P" and all accessories "OFF." Connect tachometer to engine.
2. With engine "OFF," ground ALDL connector by installing a jumper wire between terminals "A" and "B."
3. Turn ignition "ON" but DO NOT start engine. Wait at least 45 seconds and disconnect IAC valve connector at throttle body. Disconnect timing set connector to put electronic spark timing (EST) in bypass mode.
4. Timing set connector is two black/white wires joined by a white connector located under the center console between the front seats. DO NOT disconnect 4-wire connector at distributor.
5. Start engine and allow system to go into closed loop. Minimum idle speed should be 650-750 rpm.
6. If adjustment is required, use an awl to pierce aluminum idle stop screw plug, and pry out. Adjust minimum idle speed to specification.
7. Whenever minimum idle speed is adjusted, throttle position changes and throttle position sensor must be adjusted as well.
8. With engine "OFF," reconnect timing set connector and remove jumper wire from ALDL. Reconnect IAC valve connector.
Idle speed specification: 800 rpm