What happens to the ICV when the idle switch is deactivated on a C3.2?

[Tippy]

Just as the titles says, what happens?

Does it go to neutral/right in the middle, closed, or what?

Does it become part of the airflow circuit (air through it and TB) or is it totally shut off once part throttle is used and 100% of the engine's air comes through the TB only?

[aston@ultrasw.c]

It moves to the middle of its range and stays there.

[Tippy]

So air goes through it at part throttle too?

It never closes off?

[Tippy]

Originally Posted by nesslar

Do you mean when you jumper the thing at the given points? I should think it stays as it was, that's why with the jumper in place the idle can be adjusted up or down. In my experience it is an easy and effective fix. I don't see how the thing can move/change until you make it do so at the adjusting screw. I hope I know what the heck you are 'talking' about.

No, I am not concerned (right now at least) about idle speed. Trying to understand how the ICV operates once the idle switched is deactivated.

What it's purpose in life is after idle.

[aston@ultrasw.c]

When the throttle is closed a fixed amount of air is supplied through the TB.

The ICV makes small changes to adjust the idle up and down as needed.

By jumpering out the ICV when setting idle, the ICV is fixed in the middle of its range.

It is then free to move in either direction when the jumper is removed.

[Tippy]

Forget about the "jumpering", setting idle speed process.

I am talking about what happens to the ICV when the idle microswitch is deactivated. The one behind the TB.

Does the ICV go neutral (air goes through it along with TB air) or does it fully close to allow ONLY air through the TB for part throttle to WOT?

[aston@ultrasw.c]

just like you said in your original post, guess i need to work on my reading comprehension

[aston@ultrasw.c]

but it's a good guestion though....

[Tippy]

Hmmm.....I'd assume it closes?

[john walker's workshop]

see post #3.

[nesslar]

What ever. I will just add.... OK. What is the point, though; just curious. Why not let it do its thing? Why would one disconnect 3.2 stuff that makes it work? No need to respond, because it won't mean $^% to me, anyway. "I know nothiiiiing", as the good Sgt. would have said...
I REALLY would like to know, however, why this matters. Not being sarcastic or anything, just wondering. Really! Iwould guess, however, that as its name implies, it has no life after idle, goes to 'useless/centered'; except for one major thing....every engine I ever saw/heard returns to idle eventually......or dies....

[dshepp806]

Maybe maladjusting it will help you better understand it's function>? Just jack it way the frik out,....then look (measure) the situation?

A starting point (as I understand it) is set with base idle adjustments...frik this up, and one is running under maladjusted conditions (ranges)? No?

I'm always up for learning more on this stuff....(seriously).....

BEST!

Doyle

[Tippy]

I thought maybe my ICV was opening during part throttle causing my stumble, cutting out, bucking off idle when taking off from a stop and light load.

It still would be metered air but wondered if it could cause my condition.

[nesslar]

Man....don't know. Maybe yank it and clean it? Sounds more like dirty filters....has it gotten worse of late?

[Tippy]

I have a whole thread about it about a "cliff" and a "Carrera".....

[Tippy]

Originally Posted by john walker's workshop

see post #3.

So it always has air going through and never closes?

[john walker's workshop]

pull it off and blow through it.

[Tippy]

Originally Posted by john walker's workshop

pull it off and blow through it.

So, pulling it off and the idle microswitch deactivating will give the same results for what I am asking I assume?

Wasn't sure if once the idle microswitch is deactivated that the ICV is held electrically to one side closing it?

[ischmitz]

As others said: When the engine is at part throttle (IDLE open, WOT open) or full throttle (idle open, WOT closed) the ICV moves to a fixed position (not fully closed, not fully open) . In this case most of the air goes through the throttle body plus a very small part that floes through the ICV.

Obviously the portion flowing through the ICV is very small. The real reason for the ICV not fully opening or closing is to optimize its response time. Once the ICV is activated during decel process the valve body should be in an approximate spot to ideal rather than having to move there.

Once WOT and IDLE are closed the ICV moves to another fixed position. This position is its center of flow regulation. It makes sure the ICV control range is centered around the idle speed setpoint of the DME.

Think of the ICV as an adjustable bypass of the throttle body. Air going though the thottle body (and the bypass) is metered (causing the mixture to stay constant). So in other words the ICV more or lesss acts like the stop screw of a conventional throttle body. Instead of a screwdriver it is adjusted by the DME.

(The only fault with this analogy is that the effective throttle body diameter is not fixed. It varies by the ICV openining angle. This is a very small effect thus neglectable)

Ingo

[E Sully]

If not an air leak, you may have worn tracks in your afm. Air Flow Meter (AFM) - from "The 944 Motronic DME" by FR Wilk* ©2001 www.the944.com
Like you noted, icv is still metered air and would not affect mixture unless the hoses holding it have leaks.