Throttle Body: Adjustments

Model B115 Throttle Body Assembly:

ADJUST MINIMUM THROTTLE POSITION
NOTICE:
Adjustment should be performed only 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.

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 Idle Air Control (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.


ADJUSTMENT PROCEDURE
Tool required: "Scan" tool

^ Back throttle stop screw out until an air gap between the screw and the throttle lever can be seen by looking downward from above the throttle body.

^ Turn the stop screw in until it just contacts the throttle lever.

^ Turn the stop screw in 1 to 1/2 turns further.

IDLE LEARN PROCEDURE
Any time the battery is disconnected, the programmed position of the Idle Air Control (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:

^ Restore battery power.
^ Connect Tech I "Scan" tool.
^ Select "IAC SYSTEM," then select "IDLE LEARN" in the "MISC TEST" mode.
^ Proceed with idle learn as directed.

This procedure allows the Electronic Control Module (ECM) memory to be updated with the correct IAC valve pintle position, for the vehicle, and provide a stable idle speed.

INSPECT
^ Connect "Scan" tool to Assembly Line Data Link (ALDL) connector.
^ Place transmission selector in "Park" (A/T) or "Neutral" (M/T).
^ Start engine, allow it to reach normal operating temperature (about 90°C) and "Closed Loop."
^ Using "Scan" tool, observe Idle Air Control (IAC) valve counts.

NOTICE:
Battery must have been disconnected during replacement procedure and then reconnected before checking IAC valve counts. This will enable the ECM to relearn the IAC valve pintle position.

IAC valve counts should be checked with all accessories (A/C, rear defog, ect.), transmission in "PARK" (A/T) or "Neutral" (M/T), and engine cooling fan "OFF."

Make sure throttle and cruise control cables do not hold throttle open.

With engine stabilized, IAC valve position should be 10 to 20 counts. If not, repeat adjustment procedure.