Idle problem!
 

Ok so over the past few months I pulled the intake manifold, did the venturi delete in my 86 951, replaced the old vacuum lines with lindsey racing silicon lines yada yada yada. I opened up the ICV to check it while I was in there with the whole mess. It's good. Put everything back together, started her up tonight and found that it was idling steady at 3200 rpm. No biggy, pulled up the idle adjustment instructions online, adjusted the hard stop, TPS (it was way off), then put in the wire bypass to B & C ports to cut out the ICV. When I started the car the idle started searching. It goes from 800-1900 up and down and up and down. Turned the idle adjustment screw in and out and nothing changed, it just kept searching. Any suggestions? I'm at a loss and have not driven my baby in 3 months so I'd love to get her back on the road.

Did you actually take the ISV apart? If you did, that's not a good idea. You should only rinse it out with a solvent or WD-40 at most. That thing is supposed to be air tight. I suspect you didn't seal it when putting it back together and it's leaking now.

Mine had a minor leak and caused the same symptoms you describe at idle and that were fixed by replacing it with a new unit.

They can be resealed with RTV, but it's kind of a half-a$$ed fix and they end up leaking again

You can test yours for leaks by removing it from the car, capping one port with your thumb and blowing into the other. If you hear air coming out, you have a leaky ISV that will kill your idle. HTH

Yeah I opened it up and followed the directions that soxnail put in a how to write up here on the forum so it should be good to go.

When you put the ISV back together did you test it ? to make sure it was switching and also not leaking ?
You can test both by connecting an air source to the hose that goes from the ISV to the hard pipe. Now pull the connector of the ISV (it can be done without taking the intake manifold off, but is a pain). Now you can use a 9 volt battery or the car's battery to activate the valve. If you use a 9 volt battery connect the + to the center pin of the ISV, (I use alligator clip leads for this). Connect the - to an alligator lead and touch the two outer pins of the ISV, as you go back and forth the valve will kick over with an audible click. If it does not do this it is barfed. If it does click over then put about 5 psi into the hose going to the ISV from the hard pipe and do the above test. It should allow the air to pass through freely in one click and stop it on the other. Some air will leak past the valve but not much. If this works out then the valve is good. If you use the car battery IMPORTANT put a 20 ohm 10 wt resister in the loop. DO NOT CONNECT the car battery directly to the valve.
Repeat the above test.
If the valve tests good then we can start looking at other sources.
You did not state if you were able to set the idle with the ISV neutralized ?
The surge you are seeing is being caused by the car knowing that it is throttle idle (as you set the tps correctly) and sensing the rpm run away so it cuts the fuel which then drops the rpm. When it gets low enough the fuel is turned back on and the rpm starts to go back up. This is repeated process you are seeing (surging).Sox

Even when the ISV was neutralized it was still surging up and down and no matter where the idle screw was it still kept on surging. I took the wire crossover out of the B&C ports to see what would happen and nothing changed, it kept on surging. Hope that's clear enough.

This is sad I am doing this on xmas eve.....
You did not ans. the question on the isv working Please respond to the question. Did the Isv test ok or not. If it is not working then the screw or the b& c jumper are not going to do any thing.
Merry Christmas
Sox

merry christmas sox. get off the internet and go set the presents under the tree.

Merry Xmas Nize, hope Santa got your request for more HP at the wheels :)
Sox

did the test today... couldn't hear anything clicking over so i'm just gonna have the bite the bullet and get a new one i guess...

at least you've solved the problem. :)

When I cleaned up under my intake I removed the ISV and found it leaking. I cleaned it out and sealed it back up with epoxy. Now when I start the car and give it some gas and let off, returning to idle it goes down to 400rpm and feels like its going to stall and then jumps back up to 1,000. This stops after the car warms up. I'm guessing my ISV has bit the dust and will replace in the future.

Drop it in the mail to me if you want me to take a look at it.
Sox

haha... oh i hate cars sometimes... ok so i bypassed the ISV for now by turning the hard stop screw down just a little more so that it's just past the TPS click point... started the car up and all the sudden she's blowing white smoke out the exhaust and smoking on the left side of the engine compartment... i just can't get a break at all. She's also idling at 2900 and then once she starts to get warm the idle takes off to 4k.

burning oil? what color is the smoke? by 'left side' do you mean the exhaust side or the turbo side?

the smoke is a whitish brown coming out the exhaust and a white coming out the exhaust side of the engine compartment... smells like it's running really rich. I have a huntley racing fuel/air mix adjuster in the glove box, and if i dial it rich the idle drops and if i dial it lean the idle goes up... rather weird, but no matter what she smells like she's running really rich. I'm thinking bad O2 sensor or the FPR/Damper are fouled somehow?

pulled the vacuum lines off of the FPR and Damper, no fuel present in either of them so those should both be alright... how would I go about checking the O2 sensor to see if it's good or bad?

Ok slow down take a deep breath
When you turned the tps over to where it is past click point you defeated the cars "idle run away" so now your rpm is free to go to where ever the a/f ratio takes it. Before the idle switch was activating the fuel cut off. By passing one component of a loop without understanding how the whole thing works will not help solve or trouble shoot anything, don't be offended.
Your problem has not really changed.
I don't know why you have smoke in the engine that does not sound good.
One step at a time.
Sox

i agree with sox here. it seems you're just compounding the problem and making things even more confusing by skipping ahead trying to fix things without properly diagnosing it first. i know it's painfully tedious to go through all of the steps, and it's tempting to skip ahead, but in the end you'll just end up wasting a lot of time and effort and possibly damage the car.

well damn... not offended, i shoulda known better than to try a quick temp. fix, right now i just don't have money cuz i just paid for next semester so i was trying to get around having to buy a new ISV for now. so, buy a new ISV and get that working and then move on from there? Looks like the car's outta commission for another month :(

btw, it sounds like the car is running rich due to the missing idle stabilizer and forced open throttle.