ICV voltage

[r_towle]

84 carrera, 3.2
Where does the Idle Control Valve (ICV) get its signal from?
I disconnected the O2 sensor and its still fluxuating at idle.

Checked the vacuum lines.
Removed the throttle body, cleaned it, redid the throttle linkage, set the idle micro switch.....

I have yet to put an ohm meter on the micro switch but a friend of mine ( very experienced porsche shop) stated that I should look at the voltage going to the ICV to see if its steady...and not a fluxuating voltage.

So, where does the ICV get its voltage from?

Rich

[DRACO A5OG]

I believe via DME signalled by the O2S & Idle Switch at the TB.

Try removing the O2S or B&C jumper it. If it still fluxuates then you may have a AFR mixture issue. When she is hot ( proper running temps ) see what voltage you have at the O2S. It should be .5-.6 volts average. If not, you need to adjust the AFM. this is a rough adjustment, to properly adjust you need a LM-1 or LM-2 to obtain stoic 14:7.1 Air to Fuel Ratio.

I am hunting down base idle issues as well. I have checked all usualy suspects plus more i.e. PCV replacement but last thing is the Fuel Pressue Regulator, waiting on a fellow Pelican to see what he finds.

[rusnak]

To set base idle, you have to jumper two pins in the engine service socket. I'll post a pic later that shows this.

[r_towle]

setting the base idle with the idle bypass using the jumpers would not affect the bumpy idle when the O2 sensor is unplugged...
The O2 is not getting a signal back to the DME....
Even then, the ICV should not be doing anything...its not being told to by the DME?

My simple punt it to put in the new DME relay I have and keep the old one as a spare...cant hurt.

I am thinking fuel pressure at this point...but I have no idea.
What voltage should the ICV be seeing?
Is it a constant 12VDC?

Rich

[r_towle]

On another thought, I did see some thread on the AFM getting scored on the contacts but it was not idle related...it was something else to do with a bumpy acceleration.

I may take that apart to look...not sure I really want to.

Rich

[DRACO A5OG]

Originally Posted by r_towle

setting the base idle with the idle bypass using the jumpers would not affect the bumpy idle when the O2 sensor is unplugged...
The O2 is not getting a signal back to the DME....
Even then, the ICV should not be doing anything...its not being told to by the DME?

My simple punt it to put in the new DME relay I have and keep the old one as a spare...cant hurt.

I am thinking fuel pressure at this point...but I have no idea.
What voltage should the ICV be seeing?
Is it a constant 12VDC?

Rich

Oh no, the O2S should be plugged in when B&C jumpering to check and set base idle.

ICV should still get a signal from the DME, regardless.

It might be the FPR, that is my last suspect on my baby after finding my Vaccum leak using a SMOKER at the Mechanic's Shop.

ICV has a 12V input source, a Signal Source and Ground. Have you verified the OHMs on it per Bentley?

[DRACO A5OG]

Originally Posted by r_towle

On another thought, I did see some thread on the AFM getting scored on the contacts but it was not idle related...it was something else to do with a bumpy acceleration.

I may take that apart to look...not sure I really want to.

Rich

Oh No, if it aint broken don't fix it. Leave it alone, the mount for the screws are very fragile behind the black cover.

[steely]

I copied the info below from a post here - I regret I cannot provide the proper credit.
If you disconnect the connector, you will only be able to read the +12 and it will be difficult to see the low side driver signals w/o getting a little fancy.
hth

[snip]
The ICV on a 3.2 is a three-terminal device. It has two coils with one common input and two individual inputs. One coil moves the IVC the its open position and the other moves it to its closed position when energized.

The common input is connected to +12V. The signal to the other two inputs is a square wave signal 180 degrees out of phase. Essentially, one signal is the inverse of the other. It's a low-side driver with two outputs providing a path to GND. The frequency of the signal is fixed at 80Hz. The duty cycle of the square wave determines the opening angle of the valve. At 50% it is in its centered position. The DME on the 3.2 uses a microswitch to sense when the throttle input is at idle. That is when the ICV actively regulates air. Once the throttle is depressed the ICV moves to its center position.
[snip]

[rusnak]

Here's how to set base idle: see pic. The icv gets signal from the dme.

Not sure if this will solve the idle problem though. For sure, check the idle switch adjustment and function with an ohm meter, and then check closed loop operation with a fuel air gauge, such as an LM-1.

[DRACO A5OG]

Nice, if I may add, if Chipped i.e. 911Chip, 84-89 base idle would be 880RPMs

[Lorenfb]

"Where does the Idle Control Valve (ICV) get its signal from?
I disconnected the O2 sensor and its still fluxuating at idle."

With both disconnected, the idle should be stable and NOT requiring the
adjustment setup procedure as mentioned in this thread. Focus on finding
what's causing a most likely rich mixture and NOT air leaks which generally
cause a low/weak idle, i.e. an air leak after the AFM.