Hi IDLE 1986.5 S2 /3

[aluminum]

Its been awhile since I Used this car much But it runs and drives Fine except for A Hi Idle situation:
Some months back a Mouse decided to nest under the intake manifold near the MAF
Anyway I removed the nest and dead Body as I had poison bait in the garage.

The Car always ran perfect since I did a front end refresh some years back.
Much to my surprise when cleaning out the nest I discovered that the Rubber Hose that
seems to run from a Valve that's perhaps the Idle Control Valve ? up to the Center Air Plenum
Larger section of the Intake Tubes and connects to bottom of that center tube.
"The Rubber Hose was completely destroyed and rotted out and wide open to suck air "
( Yet the Car idled fine like that ??? )
That Rubber hose is about 6 to 8 inches long and about 1.5 inches in diameter at lower large end and about 1 inch at the Top end.
I ordered a New one and installed it
( all other rubber hoses Looked Fine as did the MAF)
Started the car up and it Idled fast the choke I thought but as it warmed up
the Idle was at about 1,200 RPMs
I drove the car some miles and it still runs and drives fine except the fast Hi Idle ?
So then I tried to slow the Idle Via the adjustment in front discovering it was already turned all the way in ( 7 MM socket CW )
So My Question is how can I get the Idle Back Down to 675 RPMs and does that Hose hook to the Idle control Valve ? or is that something else ? I thought that hose is to suck fumes from the crankcase ? not sure ? is that what its for ?
Perhaps that Valve (if it is a valve ? ) is stuck open or shut?
Any Help appreciated

[Matt at Pelican Parts]

It looks like there's something called an "idle stabilizer valve" that you may want to check into. It's supposed to be fully open when cold and fully closed when warm. I found a thread here which links to a YouTube video on how it operates:
High idle

[aluminum]

Originally Posted by Matt at Pelican Parts

It looks like there's something called an "idle stabilizer valve" that you may want to check into. It's supposed to be fully open when cold and fully closed when warm. I found a thread here which links to a YouTube video on how it operates:
High idle

The Idle Control Valve ( sometimes called" stabilizer ")on a 1985 and 1986 & 1986.5 S3
Like mine ( 86.5 S3 That's a 32 Valve motor ) are different then a Early Type and also then a late type ( S4 ) I am reading.
You don't have to pull the Manifold to remove it.I removed it just a few mins ago and as I read it has 3 Terminals hooking to the Porsche 928 Wiring indeed.
The One I removed I have not Checked Yet but I can check basic Functions as I already
(read last night Net) it has 3 Terminals and the center one is ground is 12volt .
Other 2 terminals are Open and Close , you can view inside somewhat from the Ports
I shall test it after a bite for lunch.
Note Idle Speed adjustment :
Their is an Idle adjustment I read and I tried that no Luck as it was all the way Down
CW but the Motor Kept racing Badly, As A test I open the adjustment Up some CCW
and the Motor speed increased went to 2000 RPM's
Shut it down and removed the adjustment ( Brass ) and I am not sure its really an adjustment but perhaps ?
This Adjustment is in front of the Main intake Body direct into the motor See Photo
attached . Black Handle with extension to turn a 7 mm socket to adjust

The idle Control Valve I just removed fits the Car perfectly , wiring plugs in Etc.
However I just ran the Bosch Number on it 0 280 140 509
and its from a 1989 BMW to a 1993 BMW so easy to get at salvage ( these 928 Bosch
OEM Valves are Very expensive like hundreds Etc .
The BMW Valve I looked up says Fits see below
interesting yes and its a Bosch not some China Job
Most Likely I can get one at Pick-pull for Very Little .
****************************************
So after fooling with a 75 SEL I am about to sell ( to many nice cars lol )
Looked at the Idle Control Valve and could see it would be Hard to open up .
So I held it with the Motor end up and sprayed Some PB Blaster into the 2 ports
that the Hoses attach to then Blasted it with compressed air, Hooked it to a battery
and began firing the end 2 terminals ( are 3 terminals center is the ground
I could feel a pulse on one end but nothing /I began banging it on a wood block
and more compressed air and kept trying it suddenly I saw it Close :
Is a sort of Barrel sleeve that rotates Right and left.
Try as I did for some 15 Mins I could get to Move in both directions but only if I started it a little
would it continue . Seemed clear to me replacement was the best option to swap it out.
What I could not understand was why the Car seemed to Idle just fine before I discovered that
The Idle Control Valve "Hose was completely destroyed and wide open with one end missing
so that it had to be sucking air sucking Air ( Not crankcase fumes ) right into the Large Center Air plenum
of the Intake Manifold the main Vacuum source for the ICV. My Guess was that the ICV had to be closed
or almost closed the entire time since I bought the 928 /So allowing it to idle OK but most likely not perform
correctly through the RPM Range.
The EUC tells Valve when to open and shut back and forth as the Motor runs quite ingenious German engineering


compatible with 62 vehicles : the BMW Idle Control Valve Bosch 0280140509 that was on it
Further investigation I found in fact this unit is also for a 1985 /1986 Porsche 928 ! so the right one.
1993-BMW-535i-Base Sedan 4-Door-3.5L 3430CC l6 GAS SOHC Naturally Aspirated
1993-BMW-M5-Base Sedan 4-Door-3.6L 3553CC l6 GAS DOHC Naturally Aspirated
1992-BMW-535i-Base Sedan 4-Door-3.5L 3430CC l6 GAS SOHC Naturally Aspirated
1992-BMW-735i-Base Sedan 4-Door-3.5L 3430CC l6 GAS SOHC Naturally Aspirated
1992-BMW-735iL-Base Sedan 4-Door-3.5L 3430CC l6 GAS SOHC Naturally Aspirated
1992-BMW-M5-Base Sedan 4-Door-3.6L 3553CC l6 GAS DOHC Naturally Aspirated
1991-BMW-535i-Base Sedan 4-Door-3.5L 3430CC l6 GAS SOHC Naturally Aspirated
1991-BMW-735i-Base Sedan 4-Door-3.5L 3430CC l6 GAS SOHC Naturally Aspirated
1991-BMW-735iL-Base Sedan 4-Door-3.5L 3430CC l6 GAS SOHC Naturally Aspirated
1991-BMW-M3-Base Coupe 2-Door-2.3L 2302CC l4 GAS DOHC Naturally Aspirated
1991-BMW-M5-Base Sedan 4-Door-3.6L 3553CC l6 GAS DOHC Naturally Aspirated
1990-BMW-535i-Base Sedan 4-Door-3.5L 3430CC l6 GAS SOHC Naturally Aspirated
1990-BMW-735i-Base Sedan 4-Door-3.5L 3430CC l6 GAS SOHC Naturally Aspirated
1990-BMW-735iL-Base Sedan 4-Door-3.5L 3430CC l6 GAS SOHC Naturally Aspirated
1990-BMW-M3-Base Coupe 2-Door-2.3L 2302CC l4 GAS DOHC Naturally Aspirated
1989-BMW-325i-Base Convertible 2-Door-2.5L 2494CC 152Cu. In. l6 GAS SOHC Naturally Aspirated
1989-BMW-325i-Base Coupe 2-Door-2.5L 2494CC 152Cu. In. l6 GAS SOHC Naturally Aspirated
1989-BMW-325i-Base Sedan 4-Door-2.5L 2494CC 152Cu. In. l6 GAS SOHC Naturally Aspirated
1989-BMW-325is-Base Coupe 2-Door-2.5L 2494CC 152Cu. In. l6 GAS SOHC Naturally Aspirated
1989-BMW-325iX-Base Coupe 2-Door-2.5L 2494CC 152Cu. In. l6 GAS SOHC Naturally Aspirated

[Matt at Pelican Parts]

Ok so if it's an idle control valve we are discussing then they are actually very simply to clean. No need to open it up.

I've had many old bmws using bosch ICV's that needed cleaning. If you simply soak the mechanical valve end in some sort of degreaser (purple power, solvent, etc.) over night it usually frees up the flap inside. you should be able to hold it and move your wrist and feel the valve inside clanking back and forth. I would suggest trying this before seeking out a whole new unit.

Also the rubber hoses attached to it should be check for cracking as leaks would also cause the ICV to operate funky.

-Matt

[aluminum]

Yes the ICV Can be cleaned just be careful not to get the Motor End Wet / Moist.
Also I researched that is some kind of Temp Switch I think that works in conjunction with ICV

Basic Operation I believe is that with " Motor COLD " the Valve is wide open and Fully warmed up completely closed. With it wide open induing a Vacuum Leak like situation the Motor speeds up Thus becoming the Choke until Warmed up,Valve closes Idle becomes Normal .

After driving the car The ECU learned my fooling with the ICV and I retested the Main intake Idle adjustment and found that indeed that it does set The idle speed very effectively

All in All this is a much better system then a lot of Mercedes have that work from Heat from the motor. AAV valve (Auxiliary Air Valve) That system works off the water in the cooling system
and takes to long to slow down also very hard to service .

The Porsche ICV system by my testing tell me that that its ether Open or closed once 12 volts hits it then it moves all the way not slowly but all at once I believe unlike the Mercedes System moving slowly a little at a time rather then all at once.
I agree with Matt that to soak the Mechanical End may get a ICV unit working again.