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The "constant idle speed" system, called CIS (and other things), automatically controls the idle speed by actuating an electronically controlled air vale that bypasses the throttle butterfly.
If the engine slows slightly at idle, as happens when cold or with the AC on or when the alternator is charging the battery, the CIS motor (sometimes called the IAV, idle air valve) opens to admit more air to the engine.
If the engine speeds up slightly at idle, the CIS motor closes the valve a bit, cutting down the air to the engine and restoring idle speed.
The system is engaged by the throttle switch, which clicks on only when the throttle is at idle. Thus, it is inactive unless the throttle is at idle position.
On an '82, the CIS motor is mounted over the valve cover. It's about the size of a small soup can, and has an electrical cable and two large hoses (about 1" diameter) connected to it.
When the CIS motor gets gummy or varnished up, it responds slowly to its electronic signals, so its response lags the drive signal to it. For example, when the computer tells the valve to close as the idle creeps up, the valve may stay open too long, allowing the idle to climb. Then a stronger signal goes to the valve, and it slams shut -- dropping idle too low. Then a signal tries to open the valve, but the varnish keeps it closed while the idle drops more. And so on. This overshoot, or "hunting," is called hysteresis.
Your OD relay is mounted behind the dash, under the center-right vent. Remove the glovebox (seven screws) and look in and to the left. The relay is clipped to a metal strut and usually buried under a harness. I think your relay is orange.
The solenoid is mounted on the transmission, rear left, accessible from the top. It's near the drive shaft.
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Don Foster (near Cape Cod, MA)
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