Idle speed control

[sjam]

Guys,

Hi I'm visiting from another group and am after some help...

I have an M series Turbo that has been fuel injected and uses a Ford 2.9 S-series type throttle body. I'm investigating ways of making the idle a bit smoother and I was wondering if any of you can tell me what you have in terms of idle speed control. It looks like my throttle body has a blank flange for an Idle Air Control valve, but it's not drilled - do you use this or some other way of fitting the valve?

Sorry for all the questions, but I can't find a picture of what you guys have anywhere...

Thanks,

Stu

[F908 Tim]

Ford ECU fed by info from top of two Air flow metres,an air bypass valve on the front of the plenium,and a throttle potentiometer mounted in the same place.
No direct adjustment of the idle speed by twiddling a screw is possible but both airflow meters have an adjustable screw for richer/weaker mixture.

Hope that helps a bit?

[tvrgit]

I have an old idle valve lying around at home - I'll try find it and take a couple of pics later so you can see what the fitting looks like.

[sjam]

Many Thanks Guys.

Ah, so the idle valve is mounted on the plenum rather than on the throttlebody itself. As its purpose is to bypass air around the butterfly, any idea where it pipes into upstream of the throttlebody?

I'm surprised it doesn't just use an RPM signal to control to, but if it works.....

Stu.

[tvrgit]

The ISCV bolts onto the throttle body and covers a drilling each side of the throttle butterfly. It controls how much air is allowed past, and hence the idle speed. It is effectively an electronic bleed screw.

The photos will explain!

[Wildfire]

So what does the bottom one do then?

[Colin Blues2]

This is a picture showing the throttle pot and idle valve on my car - hope that helps



Colin

[tvrgit]

Can't find the one I had lying around - it's too dark.

I found this diagram below though, which is generic (not specificaly the 2.9) but shows the layout of the main components in the system. No 13 is the ISCV, and you can see that it controls an air bleed around the throttle.

On the 2.9, the two drillings are above each other as Wildfire says (about 10 mm dia each IIRC) - look inside the throttle body and you see one is channeled forwards outside the throttle, and the other backwards to the plenum - so air comes in the bottom, through the valve and out the top (or maybe the other way around, I can't remember which way round the channels are!)

[tvrgit]

Here's another couple of pics of the fitted valve:





Hope this helps

[sjam]

Many Thanks Guys - That makes it all alot clearer. I was hoping that I could attach an idle air bleed valve to the throttlebody alone, but I think I'm stuffed as I don't have your plenum. I think I may have to pipe something up unique to my application.

Thanks again - you've all been very helpful.

Stu

PS, if I didn't love my "M" so much, it would be an "S" for me!