Throttle Plate - PFI: Adjustments

Throttle Body Assembly:

NOTE:

^ This adjustment should only be performed when installing a replacement throttle body.
^ The idle stop screw is used to regulate the minimum throttle valve position. On original equipment throttle bodies, it is adjusted at the factory, then covered with a plug to discourage unnecessary readjustment.
^ The battery must be disconnected during the replacement procedure and then reconnected before checking IAC valve counts. This will enable the ECM to relearn the IAC valve position.
^ IAC valve counts should be checked with all accessories (A/C, rear defog, etc.), and engine cooling fan OFF.
^ Make sure the throttle and cruise control cables do not hold the throttle open.
^ With the engine stabilized, IAC valve position should be 10 to 20 counts. If not, repeat the adjustment procedure.

CAUTION: The minimum throttle valve position is critical to vehicle performance and component durability. If the throttle valve is adjusted too far open, it will cause the IAC valve pintle to constantly bottom on its seat and result in early valve failure. If the throttle valve is not open far enough, the vehicle may not start in cold weather or may stall during warm-up.

PROCEDURE:

1. Back the throttle stop screw out until an air gap between the screw and the throttle stop lever can be seen by looking downward from above the throttle body.
2. Turn the stop screw in until; it just contacts the throttle lever.
3. Turn the stop screw in another 1 1/2 turns further.
4. Perform idle learn procedure.


IDLE LEARN PROCEDURE: Any time the battery is disconnected, the programmed position of the IAC valve pintle is lost, and replaced with a default value. To return the IAC valve pintle to the correct position, perform the following procedure:

1. After restoring battery power, connect the Tech 1 "Scan" tool.
2. Select "IAC System," then select "Idle Learn" in the "Misc. Test" mode.
3. Proceed with idle learn as directed.
^ This procedure allows the ECM memory to be updated with the correct IAC valve pintle position, for the vehicle, and provide a stable idle speed.

NOTE: Continue when complete.

5. Place the transmission selector in "PARK" (A/T) or "NEUTRAL" (M/T).
6. Start the engine, allow it to reach normal operating temperature and "Closed Loop" operation.
7. Using the "Scan" tool, observe the Idle Air Control (IAC) valve counts.