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idle control valve

A few weeks after my grand tune-up on my 85 911, it was running terrific. All of a sudden when I start it no matter if cold or warm it idles high them drops down and has rough idle. I removed the idle control valve and cleaned it but I need to know if the moving parts inside need to be set a certain way before on re install. I cleaned it well but now it is idling up down all over the place! Thoughts? Nick
Old 03-12-2018, 02:14 PM
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hi..1st thing comes to mind you have a vacuum leak...the icv goes in only one way do you have it right?
Ivan
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Old 03-12-2018, 02:33 PM
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Yes, cleaned it twice, shook it hard, heard the moving parts. put it back in, hooked it up and idle is all over the place. so i gave it a tap with a rawhide hammer and it fell back down to a lower idle. I am very bummed because the ICV costs a bunch. I wonder if it would hurt to spray a bit of PB Blaster in the valve? Silicone did not do the trick. I cleaned all of that out after I tried it.
Old 03-12-2018, 02:55 PM
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Be sure that the closed throttle micro-switch is being depressed. If not, the idle valve won't kick in.
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Old 03-12-2018, 02:56 PM
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Thank you very much John. But could you tell me where the closed throttle micro switch is located? Thanks.
Old 03-12-2018, 03:12 PM
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Behind the throttle housing, left side under the throttle lever assembly, and the lead comes around the right side of the housing to a 2 prong black plug. You can check open/closed with an ohmmeter at the plug. You can hear a click just as the throttle is opened and closed, engine off.
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Old 03-12-2018, 04:12 PM
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Just happen to have my manifold off so here is a picture of it. I would hook an ohmmeter across it to make sure it is working. Good luck!

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Old 03-12-2018, 04:16 PM
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Thanks!you guys are the best! May have a new ICV in my future.
Old 03-12-2018, 05:24 PM
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Nick .the direction of the icv is important.does it hum when you just put the key on?The best is to clean with carb cleaner.
And yes the micro switch is very important..you did not play with your throttle linkage,right?

Ivan
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Old 03-12-2018, 11:14 PM
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Ivan, I think the ICV is toast. I took it out and cleaned it. Then I clean d it again and shook it to hear the parts move inside. Oiled with a bit of silicone and reinstalled. The idle was all over the place! So right now it is very rough idle at about 8 grand then after a bit it drops to about 6. Also yesterday it was at a higher idle and a slight tap with rawhide mallet dropped it down. I have a new valve on order!
Old 03-13-2018, 01:06 PM
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Quote:
Originally Posted by Nick Triesch View Post
Ivan, I think the ICV is toast. I took it out and cleaned it. Then I clean d it again and shook it to hear the parts move inside. Oiled with a bit of silicone and reinstalled. The idle was all over the place! So right now it is very rough idle at about 8 grand then after a bit it drops to about 6. Also yesterday it was at a higher idle and a slight tap with rawhide mallet dropped it down. I have a new valve on order!
8 grand= 8 000. Your idling at 8 000 rpm? Just because you a bad idle doesn't mean it's the ICV. There are a lot of things that can contribute to a bad idle.
Old 03-13-2018, 01:45 PM
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Ivan, The car starts with idle all over the place. Then when warm, it goes up, then down, then up, then down. Car ran perfect after my tuneup two weeks ago . Then on our drive to the mountains, I noticed the rough idle. Got a good deal on a ICV so we shall see.
Old 03-13-2018, 02:42 PM
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Sorry 800 rpm. I’m a goof!
Old 03-13-2018, 02:46 PM
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Nick, do you have any idea on how to adjust or set your base idle speed? If not set right it will make you think you have a bad ICV (possibly purchasing parts you may not need) causing your idle to be all over the place. The fact you say your idle is all over the place is telling me that your ICV is working and being controlled by the DME.

Just a thought since there has been no mention of this critical adjustment.

Cheers,
Joe

Last edited by stlrj; 03-15-2018 at 06:07 AM..
Old 03-15-2018, 05:56 AM
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Hi joe. No I do not know how to adjust. I ordered the valve because I got a great deal. My thought is after 7 years of a very fine idle at 800 rpm, why would it change? Nothing was touched. Just regular tune up. But it new ICV does not smooth things out, adjusting idle speed will be next. Also, my idle was fine for two weeks after my tune up. I came to a stop on a 200 mile trip and noticed the lower rough Idle . Btw, the car runs great at speed.
Old 03-15-2018, 06:15 AM
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Nick..i have asked above if ..when you put the key on the icv should be humming-vibrates..is it? If yes it is ok.

Also does your micro switch click when you lift the throttle a little?Engine off.
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Old 03-15-2018, 09:44 AM
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Yes, micro switch does click when i lift the throttle a bit. And yes, the ICV does hum and vibrate when key is on. But even so, can't it be stuck inside and not working smoothly? This morning, I turned the key to start, it coughed and sputtered. I turned it right off. turned key again and it started more normal but settled into a much lower idle. About 550 rpms.
Old 03-15-2018, 10:49 AM
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Before all of this my car had a nice smooth idle of 800 rpm's I keep looking if I touched something. But everything looks ok.
Old 03-15-2018, 10:52 AM
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hi Nick..that sounds ok...but as i said in the beginning double check your hose clamps..it sound like you have a vacuum leak.....you did something while doing the tune up is my last guess.....let`s find the culprit...!!;-)
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Old 03-15-2018, 11:08 AM
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Bad CHT? Could be a lot of things.
Old 03-15-2018, 11:33 AM
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