3.2 idle control valve go bad
 

Last summer I got some problems with my 3.2 idle control valve....(see thread below)...After cleaned it, it working very well for some time. Now the problem is back...I cleaned it again...and all is OK again. Question is: what cause the ICV to get dirty to the point I have to remove and clean it regularly....Thanks for the imput...!

http://forums.pelicanparts.com/porsche-911-technical-forum/370635-carrera-3-2-idle-fluctuation.html

1. Dirty or torn air filter? (allows more dirt and oil vapour to get thru)
2. ICV just old and beginning to fail?
3. You mentioned you lubed it after cleaning... just clean it w/ carb cleaner and let it dry. Don't want or need an oil film on it.
4. gremlins.

maybe it's the electrical contacts, and removing it and reinstalling re establishes the connection? I dunno, I'm reaching here.

I'd think about getting a new one and keeping the old as a spare if it happens again

That was my conclusion after cleaning mine and practicing my "stop light heel/toe" technique for several months as the poor idle condition returned. 24 years is a pretty good run :). I replaced mine, idle is perfect now...

Yup....look like I'll need to buy a new one...Thanks for the imput guys.

I too removed and cleaned my ICV last year with success. I didn't disassemble it just blasted carb cleaner and shook it around for a bit until I heard the rattling noise. This year I had another stalling problem so I purchased and put in a new ICV. Problem solved. Prior to installation I noticed when shaking the new valve and comparing to the old the rattle was similar. I'd read this was one way to determine if the valve was clogged. So I decided to take apart the old valve and examine. Not sure what I'm would be looking for but I did notice the top shaft / barrel is extremely galled up. Is this normal? Just doesn't seem like the small copper contacts in the valve cover would easily cause this. http://forums.pelicanparts.com/uploa...1210008502.jpg

I assume when you mean dirty you mean sort of oily? If so one possible cause is the black rubber pipe (about 1" diam) that runs from the oil filler neck to the back of the Throttle body. This is a breather pipe that collects gasses from the oil tank and burns them. If you disconnect this pipe at the oil filler neck and then look into the pipe you should find a brass funnel device in the pipe, this is a restrictor to restrict the amount of air that is sucked out of the oil tank if this is missing you may/will take in to many gasses from the tank as well as possibly oil. Also if the rings are weak then the blow by around the piston tends to presurize the oil system and induces extra gasses into the Throttle body via this pipe.

How does the throttle body look? is it as dirty as the ICV? I'd suspect it should be. And if it is then you have oil in the intake and the only way I know oil can get into the intake is via this breather pipe.

My 84 Carrera is extremely clean in the intake and stays this way all the time. I suspect the issue has to do with oil getting into the intake via this pipe. Does the engine have poor leak-down or compression?

Just a few things to think about.

Since the air filter box is not there anymore (conic filter installed) this pipe end is plugged with a small filter in the engine compartment. The throttle body is clean....the ICV is dirt...like oily stuff....???

Thanks for the info....when I'll install the new ICV...I'll check this and will give you back some info about it.

Are you sure this pipe is plugged? The pipe I'm reffering to goes from the top of the oil filler neck to back of the 90deg rubber boot that sits between the AirFlowMeter and the Throttle body. So even if you went to a cone filter (I have a cone filter as well) this pipe should still be connected from the oil filler neck to the 90deg boot.

On the back of this 90deg rubber boot is the pipe from the oil filler neck and on the front of the boot is the intake pipe to the ICV. This is why it's a straight shot across the inside of the boot for the oil tank fumes to go straight into the ICV input pipe.

Hope this makes sence.

Here's a picture to help locate the pipe from the top of the oil filler neck to the back of the 90deg rubber boot:

http://forums.pelicanparts.com/uploa...1210084022.jpg

Sory Sal...I was thinking about the pipe that goes to the air box...I will check this line tonight and will give you feedback on my find.Thanks a lot for the info.

Syl, nothing to be sorry about.

If the ICV has oil in it this pipe is the most likely source. Since it feeds directly into the same rubber boot that the ICV input pipe is also connected to.

The important thing to check is the pipe at the end that connect to the oil filler neck, inside this end you should find a brass funnel. Be sure it's there and also that it's installed correctly and has not somehow gotten crossed up.

Also inspect the inside of the pipe in general to see how oily it is as well.

Keep in mind that as the engine ages and compresion drops it tends to pressurize the oil system and more oil/fumes are collected via this pipe.

That looks like wear from years of moving. I wonder if this could be polished out. Was the disassembly destructive to the housing? If not you might try and polish it, reassemble and see if you can extend the life of the ICV that way.

Ingo

ischmitz
 

The galling appears (to me) too deep to polish out. I'd probably have to take down 0.02 - 0.025 worth of material which I would imagine would negatively effect the operation. I was just wondering if those who have taken these valves apart have seen the same condition. I might do it anyway since the old valve isn't needed now.
thanks

I have had mine opened as well but it did not look like that. But I'm also not certain how old mine is since I bought the car 2 years ago.

You may find this thread of intrest, it's howto bench test the ICV. I did this work about a year ago:
http://forums.pelicanparts.com/porsche-911-technical-forum/360766-bench-testing-carrera-idle-control-valve.html

regarding the ICV getting gunked up... I think this may have been mentioned.... the crank case vent is across the way from the ICV pickup.. all sorts of oil fumes and even oil can come down and then across there...some goes across and goes through the ICV gunking it up. If you take off the MAF sensor and big black boot/etc. and then take off the throttle body... you will probably see a good amount of "soot" on the walls. This is the soot that gunks up the ICV... that's my theory anyway. I thought hey... it shoud be nice and clean in here... but it's not.

Cool... I was wondering how those worked. Are there two wires going to those slip rings from the rotor? Does each slip ring cover 180 degrees? Where does the third wire go (+12v)?

That galling may be metal transfer from arcing.

the center wire is 12v the two outside contacts are grounds for the two "poles".
it works like two motors.... when one side is grounded the valve flips closed when the other grounded the valve flips open.... there is a PWM driver in the ECU that decides how much time should the valve be open or closed depending on the idle speed.

by looking at your contact.. seems like you should get a new ICV...I'm not real sure why this started arcing.. most likely the contact in the body got worn out.. others may know more about this...

I was after how the current flows through the rotor to make the field point one way when one control is grounded and the other when the other wire is ground. Are there three wires on the rotor?