How do I set throttle screw

I'll be happy to give you some general info and a ballpark way to set up your throttle body

First thing is, that allen screw is not your idle speed adjustment screw. It is an air bypass screw that works along with the isc.

Second thing is, the screw on the side of the tb. That also is not an idle speed adjustment screw. That screws purpose is to keep the throttle body blade from sticking to the bore of the tb when the skinny pedal is slammed shut.

The idle speed is controlled by the pcm.

If you have either or both of these two screws very far away from their optimum range of adjustment, the pcm will compensate and attempt to set your idle speed to the pcm programmed value.

There are good articles on this forum with all the details but here is the ballpark setting I promised that will get you started.

Back off the linkage screw until it no longer touches. Tighten 1/2 turn past the contact point.

Completely close (don't tighten it hard ... just to point of contact) the allen bypass screw. Open it 1 and 1/2 turns.

Do a pcm reset with these steps ..................

Disco the neg batt cable
Turn on the headlights for 10 seconds
Turn off headlights
Reconnect batt cable

Drive around enough to where you have a combined idle time of about 30 mins to give the pcm time to adapt to various idle driving conditions.

If the idle is not stable at this time ....................

DON'T hose with the linkage screw!

Turn in or out, the bypass screw 1/4 of a turn for each adjustment giving the pcm time to adapt before trying another adjustment.

Thats how I'd do it

Grady

1smoothmustang said:

when u say at the end to turn the screw in small increments and give the pcm time to adapt did u mean to go back through the disconnecting of battery, turn on headlights, etc or simply give it a few moments to settle in to the new adjustment? thanks for the time. been alot of help

Click to expand...

at that point you would not disconect the battery. give it a day or two before the next adjustment if necessary.

I would also add (to the wise posts before me) to write down EVERY adjustment you make. I 'hosed' with my bleed and throttle-stop screw out of necessity - and as Grady said, you can get into no-man's land with the settings if you dont watch it.

I found that if my bleed was out more than about 2 turns, I had a simulated vacuum leak (hanging idle, etc). So I ran it out to the verge of that and forgot about it. Then I used needlenose pliers to mess with the throttle stop screw.

We all know Grady is smarter than I am, but I personally dont see an issue with playing with the TS screw if you WRITE down what you did since you can go back to square one if needed. I put a scribe in mine to locate "12 o'clock" and only made adjustments to the nearest 1/2 turn (I'd stop at 12 or 6 o'clock).

I also chose to make an adjustment and drive it a day. Then adjust again the next day. It took about 5 days to get it right. I dont feel you can get an honest read on how it will idle in just a couple mins (to incorporate how a rolling idle will be, high load idle with PS and brake lights working, etc).

We all do things differently so take what you will from each. And good luck!

well i might need to change mine since my car after installing my cobra intake manifold is sitting at 650 rpms, which i believe is low but if it is not let me know

Dan, that's a hair low for an AODE AFAIK (that is while in Drive, right?).

But if you dont have any voltage drop issues with a full electrical load, I personally wouldnt sweat it.

Just MHO. Good luck.

The bleed screw can make your Stang idle really hokey, hurky jerky, or in other not desirable ways if you get it too far closed/open.

Using that little fast & nasty method above, here is something I might should'a said but took for granted it was understood.

Say you did not get a stable idle after the first pcm learning period.

Open or Close 1/4 of a turn

It don't make no never mind which way to start

If after the second pcm learning period ... it got worse ...
you went the wrong way

No biggy ... just turn it back the opposite way 1/4 of a turn and you are right back to where you started

Now go 1/4 trun more and see what happens.

Like Granpaw always said ... "Just common Horse Sense"

btw ... with this kinda thing, a pcm reset between adjustments is not needed IMHO.

Grady