MFI idle adjustment screw

targa911S · 10-24-2003, 11:46 AM

I am trying to adjust the mixture at idle on my 2.2 car with MFI. The adjustment screw is spring loaded and can only be reached with the proper tool, which I have. The problem is that the manual says to press the screw in and adjust clockwise or cclockwise for adjustment. Well I cannot feel the screw "seat" in the screw slot for one, and I cannot seem to feel any "clicks" as they say. So to all you MFI pros out there, am I doing something wrong and also can the plate that the external adjustment screw is attached to be removed with the pump still on the engine?

Rot 911 · 10-24-2003, 11:49 AM

Finally a serious thread. I could never feel any "clicks" on my MFI either. To get the screw to seat sometimes you have to turn it until it pops in. Imagine you had a flat tip screwdriver at right angles to the slot in the screw. You would have to keep turning the screw driver until the tip lined up with the slot.

tobluforu · tobluforu's Garage

I agree w\kurt. Get the right angle through the fan. Press in and turn. You will feel it when you hit pay dirt. Then turn to your hearts desire. I find that this adjustmnet does not do to much.

power · 10-24-2003, 09:28 PM

The Idle adjusting screw is a phillips head machine screw (hextagonal in shape if I recall correctly) that sits in between two thin metal flat pieces that ride against the side of the screw head. These flat metal pieces are being pushed against the side of the screw and create a "clicking noise when the hex head turns between them. I also believe the thin metal pieces help guide and shield the idle adjusting screw from the other four adjusting screws immediately around the central Idle screw (these other screws are adjusted at the factory to calibrate the pump and should not be touched). Sorry for being so long winded I am trying to shed some light on the "clicking" not "clicking sounds. IMHO the Idle screw "clicking" mechanism on the idle adjuster is not as "robust" a mechanism as the part load adjuster "clicking" mechanism. This Idle "clicking" mechanism sometimes wears out and fails to produce a noteicable "clicking" noise anymore, but does not effect ones ability to adjust the idle. You should be able feel the phillips head engage the slot for adjustment, although if the srew is bottomed out it can sometime be very difficult to turn! it can really stick sometimes when adjusted all the way in.

WHCJr72S · 10-24-2003, 09:39 PM

Kurt is correct, push in and turn slowly until the tip seats into the slot. There are 6 clicks per turn of the adjusting screw. The book recomends to turn only one or two clicks at a time. Turn the tool clockwise to richen and counter clockwise to lean out. Write down which way you turn and how many clicks, incase you need to return to your starting point. After turning the adjustment screw, you may have to correct the idle speed to 900+/- 50 RPM by enenly turning the air correction screws.
Pelican has information on how to do this in the technical area.
Bill
72S

targa911S · 10-25-2003, 07:17 AM

ok I'm on the same page as you all, but, it does not seem to seat in the slot. Hit pay dirt as someone put it. I tried last night seemingly forever to get it "in the slot" but to no availe. That is why I wanted to know if the plate that the spring loaded adjustment screw is attached to is removable. I want to see if there is something imparing the ability of the spring loaded screw to seat. Thanks for all your great responces.

power · 08:26 AM

Yes the plate is removable by unscrewing the two phillips head screws on either side. I always found it difficult to do with the pump in the car as oil everywhere and tight clearances to other stuff limit my ability to see. The plate comes off with the spring loaded adjuster.This reveals the Idle adjusting machine screw (the one in the middle sourounded two thin metal plates and by another four (do not touch or try to adjust these!!!) machine screws. The Idle adjusting screw is actually tensioning a long thin spring, this spring acts upon the centrifugal governer (and in turn the control rack) at low rpm. after low RPM the Idle spring no longer works and a midrange spring takes over, then at high RPM another spring acts on the governer (this is what the other four machine screws that you will see, adjust). The most common problem I have seen with the Idle screw is, like I said earlier, it is ajusted all the way in and stuck. The other problem with the Idle adjuster I have heard about is, the end of the adjuster mechanism has been sheared of somehow. Good luck! if you do find something unusual, please post for future reference.

targa911S · 10-25-2003, 12:34 PM

yes ..thanks. I was thinking something along those lines. I should be able to feel it set in the screw slot inside and I don't feel that. When I do try to turn it just blindly it does not feel at all like it wants to turn. I have a factory adjustment tool, not the cr*p set that performance once sold, so it is not a mater of not accessing the adjustment screw properly. I will try to get the screw and cover off to see whats going on inside there over the next couple of days so I will keep you posted. Thanks again for all the great info. I knew somebody out there would know.

jeff m · 10-26-2003, 05:21 AM

One thing you coukd try brfore tearing things apart is screw up a small peice of paper and put it into the socket part of adjuster this will give the the socket "less depth" and will push the head down a little more.
A long shot but only takes a minute to try.
Jeff

targa911S · 10-26-2003, 06:26 AM

yes that makes sense. I will try too. The socket does seem a bit deep, Thanks

targa911S · 10-26-2003, 11:45 AM

well Jeff your longshot paid off. i wadded up a little piece of paper and inserted it into the socket and tried it again. It worked perfect! thanks to all for your input.