Computers and Control Systems: Adjustments

IMPORTANT Minimum idle speed should only be adjusted when installing a replacement throttle body. The idle stop screw is used to regulate the minimum idle speed of the engine. On original equipment throttle bodies, it is adjusted at the factory and is covered by a concealment plug to discourage unnecessary readjustment.

NOTE Minimum idle speed adjustment is critical to vehicle performance and component durability. Incorrect minimum idle speed adjustment that is too high, can cause the IAC valve pintle to constantly bottom out on its seat, resulting in early valve failure. If minimum idle speed is adjusted too low, the vehicle may not start in cold weather or may stall during warm-up.

ADJUSTMENT PRECHECK
- Engine and transaxle must be at normal operating temperature.
- Adjustment must be made with transaxle in PARK or NEUTRAL.
- Engine operating in CLOSED LOOP mode.
- All accessories in the OFF position.
- Check to see that the throttle or cruise cables are NOT binding.

ADJUSTMENT PROCEDURE
1. Block drive wheels and apply the parking brake.
2. Connect a scan tool to the DLC connector.
3. With the ignition ON, select the Field Service mode on the Scan tool and wait 15 seconds to allow the IAC valve Pintle to seat in the throttle body bore.
4. Disconnect the IAC valve connector then exit Field Service Mode.
5. Using the Road Test mode on the Scan tool, select engine speed.
6. With the transaxle in PARK, START the engine and allow rpm to stabilize.
7. With the engine speed stabilized, rpm should be 600 +/- 50.
NOTE: Vehicles with less than 500 miles or vehicles located at high altitudes may have a lower rpm than indicated with a seated IAC valve.
8. If adjustment is needed, remove stop screw plug if necessary and adjust idle stop screw until desired idle speed is attained.
9. Turn the ignition OFF.
10. Reconnect IAC valve connector.
11. Reset IAC valve pintle position.
a. Depress accelerator pedal slightly.
b. START and run engine for 5 seconds.
c. Turn ignition OFF for 10 seconds.
d. Restart and check for proper idle operation.
12. Install air cleaner assembly.
13. Disconnect Scan tool.
14. Remove block from drive wheels.

CONTROLLED IDLE SPEED
Idle speed is controlled by the ECM and is NOT adjustable.