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Discussion Starter · #1 ·
I've been reading this board and the other also for some time now and have been amazed at the knowledge you guys have. I sent a post yesterday but it didn't go for some reason, hope it don't go twice. Here is the problems I'm having. 1) Can't keep the IAC set. I've tried both methods you guys have posted but every time I check it again it is off usually back to 00. I cleaned the TB and IAC valve but it didn't help.TPS stays put. 2) I drove the car on a trip over the week end and it did ok except on the way back it started vibrating when boost got up to about 5lb thru about 8 or 9 lb. From there on to 15 it was ok. Is this a sign that the turbo is going? Car is stock with basic mods as listed below if it makes it with this post.Thanks in advance for your help.

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87 GN KB Ram Air & exhaust,Gauges,SM2,Adjustable Regulator KB Pro2 chip the rest is stock.
 

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kinda hard to diagnose long distance but the IAC may be bad. One common problem with them that I have seen is overtightning can crack the plastic housing.

At what point are you setting it? How many counts? and is the engine fully warmed up and in Park with the ac off? Do you switch the engine off and restart to reset the iac after adjustment and is it where you thought it should be? I have seen it change if I made significant adjustements.

With regard to vibrations, hmmm, you might pull the inlet hose off the turbo and inspect the blades/housing for damage. Then reach in and grab the nut that holds the compressor blade and try to move it. there should be virtually no movement.

Check the mounting brackets for loose bolts.
 

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Not sure on the 86/87 cars, but on the 84/85's the iac has to be retracted manually if it measures more than 1 1/8" from the base of the threads (last thread as you screw it in)to the tip of the valve. I think mine was not retracted and that is why mine jumps around somewhat at idle. The 86/87 cars may be different and I have seen no explanation why it needs to be retracted on the 84/85's, but I guess it does, and I think mine is screwed up.


If anyone can shed some more light on this...



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Thanks guys for your replys!! Steve: I didn't look closely to see if the IAC was cracked or not but while cleaning it I noticed the wear pattern on the sides of the plunger(cone shaped tip) was wore more on one side than the other. I guess I will get a new one. I have been setting it at around 14 or 15 with engine warm A/C off and in park.Followed your directions to others.Shut off engine and checked again and it would be ok. I would then unplug the ECM and drive the car, this is when it would run like a scalded dog. The next day however the counts would be at 00. It wouldn't take much adjustment at all to get it back. I tried the method where you jump the tet jack insid and adjust idle for around 650 also but had the same results. I will check the items on the turbo you suggested,I was just wondering if the way mine was acting was a typical symptom when they start to go.ES: Vibrates only at 5 to 8 lb. and then smooths out from there to 15. Vibrates only under boost. Vibrates at a fast rythem that even shakes the needle of my hood mounted fuel pressure gauge.If you tromp on it and go to WOT you dont notice it but if in cruise and climbing a hill it is very evident. Zap: I don't know if measuring the plunger length will work on the 87 or not. The procedure that calls for jumping the test jack is supposed to extend the plunger and allow you to set the idle at that point. It appears that if everything is according to hoyle you would wind up with a count between 20 and 40 since the procedure calls for the car to be in gear when you set the idle. Thanks again guys for your input. I'm going out of town again tommarrow evening and won't be able to check things but will as soon as I get back, so I will be able to read any return posts you provide today or tonight. I changed the chip to a 92 thrasher by the way.

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87 GN KB Ram Air & exhaust,Gauges,SM2,Adjustable Regulator KB Pro2 chip the rest is stock.
 
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