This is a problem that's been going on for quite some time, I just haven't bothered about it until now.
My '89 740 Turbo Wagon with 110K miles starts up nicely in warm and cold weather (unless after a long rain/snow, which is a different topic - I think). When I start the engine, the RPMs go up as usual, and then settles down into normal 1000 rmp range. Then, after about 10 seconds or so, the RPMs go down into the hundreds, the engine shakes as if it tries to catch itself, and it dies. If I then start the car again, it starts fine, although it does shake a bit at first when going below 800. The longer the engine runs, the better this gets - after driving a few minutes the problem goes away completely.

Reading the FAQ points me to a clogged or faulty Idle Control Valve, or as the FAQ calls it, IAC. Since I can get this item almost new right now for very cheap, I want to know if replacing this valve is a DIY job, and if so, what are the steps to replace it. Or does the problem lie elsewhere?

Can anyone with experience in this matter help? Thanks!!

It might also be a slightly bad AMM. The AMM has many functions, and hence it can be defective in many areas with many symptoms...

Can also be the IAC valve (or motor)... Try hitting it while, this can losten it if it is stuck.

Also, while the car is idling, you can try this: Undo the hose to the intake, coming from the IAC. Quickly, plug up the intake hole, or the loss of vacuum can stall the car. See how the car idles now. If it idles different or better, then you might suspect the IAC.

Along with all this, you can also very easily have a vacuum leak somewhere in the intake. Check ALL ducts, clamps, and hoses for craks/leaks.

Not very sure, but hope can be of some help.

Greg Mustang
Montreal - Ottawa
Canada

replacing the IAC is a 15 minute job..no problem at all. But, based on what you wrote, I would not bet the farm that the IAC is the problem, or at least not the ONLY problem. More likely, the set screw for the throttle plate adjustment, the throttle position switch adjustment, and the throttle control cable are all out of whack and giving you the symptoms you describe.

But, if you can get a new one cheap, I would get it and install it. Even if it doesn't fix the problem, you have a good spare.

good luck

Of course, all that is possible but I would really like to avoid touching any adjustments especially if the car is still a virgin. It is very easy to offset one thing to cover-up something else. This is my philosophy. It often compounds future problems.

Greg

First tell me where you can get one cheap! I agree that it could also be the AMM...hope it is the IAC though. You can also try to clean your IAC without much dificulty. I have done this often with my two cars and got good results. To remove it, simply unplug the electrical connector, the two hoses and loosen the belt holding the strap around it. (also how you remove and replace btw) Take some carb cleaner and spray both holes well. I uses a little screw driver and push down the plate below the spring to loosen stuff up. Give the cleaner a little time to work...shake it up with your fingers plugging the holes. After you feel comfortable that it looks a little cleaner, reinstall. The car may sputter a bit if you did not get all the cleaner out but every time I did this, the idle returned to normal. Oh, and if you do this and the car runs like crap...much worse that before, save the hour I spent the last time I did this trying to figure out what the H is wrong and look at your vacuume hoses. I accidently pulled one loose! Good luck!