12.37. The Idle Air Control (IAC) valve can be turned using an adjustable wrench (shown in the illustration) or a 1 1/4 inch wrench
38. Remove the old IAC valve gasket. Clean the throttle body surface of the old gasket material to ensure proper positioning of the new gasket.
39. All valve shafts in IAC valves on TBI Model 220 blocks have the same double cone. However, the axles on some units are 12mm in diameter and on others they are 10mm in diameter. When replacing an IAC valve, the new valve must have the correct axle cone diameter and the correct diameter to properly seat the valve in the throttle body.
40. Measure the distance between the end of the axle in its fully extended position and the housing mounting surface (see illustration). If the distance "A" is greater than that specified in the specifications of this chapter, it must be reduced to prevent damage to the valve.
12.40. Flanged type IAC valve for injection system model TVI 220: A - extension distance of the distribution axis, B - diameter of the distribution axis, 1 - sealing ring, 2 - screw and washer
41. If you need to adjust the shaft, determine if your valve is a Type 1 (there is a flange around the electrical terminal) or to type 2 (the flange is missing).
- a) To adjust the IAC flanged valve shaft, hold the valve and push down on the shaft with your thumb while rocking it from side to side (see illustration).
- b) To adjust the IAC valve shaft without a flange, compress the retaining spring while turning the shaft clockwise (see illustration). Return the end of the spring to its original position, aligning the straight portion in the groove under the flat surface of the valve (see illustration).
12.41a. To adjust a flanged IAC valve, press firmly on the axle with your thumb while gently rocking the axle from side to side |
12.41b. To adjust the IAC valve without a flange, compress the valve retaining spring while turning the shaft clockwise... |
12.41v....then return the end of the spring to its original position, aligning the straight part in the groove under the flat surface of the valve
42. Install the IAC valve and tighten the screws securely. Connect the electrical connector.
43. Install the air filter, adapter and gaskets.
44. Connect the wire to the battery.
45. Start the engine and wait until it reaches operating temperature, then turn it off. No adjustments to the IAC valve are required after installation. The IAC valve is electrically "reset" by the ECM after the engine is turned off.
[The text of the article was obtained from the website: ChevyMan]