I've cleaned out the following on my car, and have a resulting (and common) problem with a high idle .

- Throttle-Body

- Aligned Throttle-Body butterfly valve so it closed snugly. Needed to do this as I had to remove the shaft for lubrication.

- Set the idle stop on the throttle-body to spec (1/2 additonal turn after it just touches the trottle lever)

- Installed a new TPS and set it AFTER setting the Idle-Stop. Verified TPS works fine

- Fuel-Injectors

- IAC. Opens and closes perfectly with an audible snap. Verified that valve works by blowing into it in both open and closed positions.

- Checked the AMM

- Verified O2 sensor voltage-range was healthy (0.2 -> 0.9v)

- Flame-Trap

- All hoses

After putting it together again, the idle jumped to 1500 - even with the black idle-control knob on the trottle-body fully closed. Allowed sufficient time for computer to get used to the cleaned components (just in case ?), but idle still high. I am nervous about high idles because of my delicate ZFHP22 tranny. I expected that grounding the White/Red test-point would 'CLOSE' the IAC and drop the idle so it could be solely controlled by the idle-setting knob - but it seems to do absolutely nothing.

At that point I cleaned the injectors and lubricated the seals (with ATF). Idle dropped down to between 800-1200 which I still consider too high.

Suspecting that the butterfly valve in the throttle-body was not fully closed (I can see a fine circle of light between the edges of the plate and the throttle-body - sort of like a very-fine corona in a total-eclipse) I decided to check how much of the high-idle was caused by this. I...

- Disconnected the 2 IAC wires at the big engine-wiring-harness grey-conector on the passenger-side, and temporarily shorted the white/red one coming from the IAC to ground - which fully closes the IAC

- Also made sure the black idle-control knob on the trottle-body was fully closed - which it was.

In this position, all of the idle would be controlled by air passing through the butterfly-valve. Was barely able to get the car started, and idle was around 150-300 with the engine threatening to stall at any time. Boy - that was the quietest I've ever heard a Volvo run !

So it was obvious the high idle was being caused primarily by the IAC. Which brings me to my main question.

During normal operation, does the IAC valve have just 2 positions: Fully-Open or Fully-Closed ? Or are there many levels between them ? And if so - how does the computer achieve these partially-open positions ? Is it by passing more current through the open-motor-widing than to the closed-winding ? Can this be easily checked by hooking up up a meter in parallel ?

How is the White/Red test lead supposed to work ? Is the change noticeable when grounding it ? Anyone know which terminal on the computer this goes to so I can short it at the computer itself avoiding a possible bad connection to the test-points...

Mine is an 85 740 Non-Turbo, so the only test-points are the idling & CO ones in the passenger-fender well. I noticed that there is a red-jumper wire connected at the LH Jetronics 2.2 computer box. Anyone know what this is for ? Can any codes be read from this point ?

Any responses would be much appreciated.

Thanks,

Noel