Andy1212

Ok guys heres the situation, when i start the car up cold it starts right up and idles around 950-1000, perfect. But then after about 5 minutes the idle drops to like 300-400. It never stalls, but it comes close. I can here the idle dropping at intervals, like the computer is doing it. After the car is fully warm it idles great.
The things i have done which might affect it are ISV valve (i am starting to think it doesnt work), vacuum lines, and i did the Wliks shudder stop thingie.

SoCal Driver

Early 944's have a timed cold engine idle control valve. Warm idle should be around 900 rpm. Adjust it with the large air bypass screw not the hard stop for the throttle valve.

krahmlow

It could be a vacuum leak that you missed and the ECU is trying to compensate for it. In fact, that's kind of what it sounds like to me, and it's a common problem so I would start with that, personally. If you didn't do the seals on the oil/air separator when you did the vacuum lines, that may be part of your problem. Those can cause very large leaks. And the throttle body has seals on your car, doesn't it? I found a sneaky vacuum leak on my car, btw. It was CAUSED by using silicone tubing--I wasn't getting a good seal on the fittings going into the firewall (to and from the climate control stuff, I think). Check it and mabe put a small zip tie on it to tighten things up.

Otherwise, it never hurts to do your testing: You should test your 02 sensor and DME temp sensor. I wouldn't suspect the ISV if you just changed it out. Though I think there's a way to test that, too. Could be wrong.

If all else fails, I believe your car has an idle adjustment at the throttle body. I tend to be suspicious of a car that needs adjustment for no real reason (adjusting things might mask other issues), though I'm sure there are others with different opinions, but anyway there's an idle mixture adjustment on the AFM (at least there is on the later cars). If you're going to start adjusting things, make sure you find good doc. Clark's page, F.R. Wilk's page, etc. If it begins to look like the AFM is the culprit, though, there's a possiblity that it is going out of calibration. You'll need a professional with the proper equipment to recalibrate it, as I understand things.

That should keep you busy for the weekend....

Wipeout

Andy,

The vacuum and ICV were what I was going to come in and suggest. SoCal's right on the money (as usual) for the adjustment of itle on the early; the adjustment krahmlow speaks of is for the air/fuel mixture. I have it on my '85.1 (ask schwank, I drilled the plug out this last weekend while we were working on it).

Eric may have a "working" ICV from the parts car, if you think that's going bad drop him a line.

Andy1212

Thanks guys, I have already replaced pretty much all the seals on the engine, new 02 sensor, and i have the idle set with the air bypass screw to around 950 warm. The problem is when the car is not warm but not cold. I replaced my ISV valve with a used one because i thought my old one was bad. When i got both of them out i put them in the freezer and different tests and they were always exactly the same. Could someone send me a pic of how much it should be open at room temp?
-Thanks

Andy1212

Bump?

SoCal Driver

There is an adjustment for the unit. Just read a thread on one owners extensive cleaning, test and adjustments. Now were?

Andy1212

If you could find that i would be forever grateful.

EDIT: Keep in mind i have the early, heated valve.

SoCal Driver

Only the early 944 idle control valve has the adjustment.

Andy1212

OK. There is a nut on it what does it adjust? The spring tension on the valve? I have an extra one sitting on my desk right in front of me that i dont mind tinkering with.