Throttle Body: Adjustments

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.

Model B115 Throttle Body Assembly:

ADJUSTMENT
This Adjustment should be performed only after installing a replacement throttle body. The idle stop screw is used to regulate the minimum throttle valve position. At the factory, the original equipment throttle bodies are adjusted and then covered with a plug to discourage any unnecessary readjustments.

1. Back the 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.
2. Turn the stop screw in until it just contacts the throttle lever.
3. Turn the stop screw in 1-1/2 turns further.
4. Perform the Idle Learn Procedure.

Idle Learn Procedure
^ Install the Tech 1 "SCAN" tool.
^ Ignition "ON" engine "OFF".
^ Select the "IAC SYSTEM", then "IDLE LEARN" in the "MISC. TEST" mode.
^ Proceed with the idle learn as directed by the Tech 1 "SCAN" tool.

5. Connect the "SCAN" tool to the Assembly Line Data Link (ALDL) connector.
6. Place the transmission selector in the "Park" (A/T) or "Neutral" (M/T) position.
7. Start the engine, allow it to reach normal operating temperature (about 90°C) and "Closed Loop".
8. With the engine stabilized use the "SCAN" tool and observe the Idle Air Control (IAC) valve counts.
9. The IAC valve position should be 10 to 20 counts. If not, repeat the adjustment procedure.

NOTES:
^ Make sure the throttle and cruise control cables do not hold throttle open.

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