Setting Mechanical Throttle Stop - How?

[sefeing]

Hi folks!

Finally got around to doing a throttle body reseal during a warm day here in NY using the Tom/Arnnworx kit, and remembered that once upon a time, a shop had incorrectly adjusted my mechanical throttle stop.

Since I have the intake and TB off the car, I'd like to take this opp to correctly adjust this, so that all idles right.

Is there any guide to how to set this stop? If it's threaded too far out, the plate sticks in the bore, too far in, and i'm sure the idle will be higher than expected.

IMG_2538.JPG (2.27 MiB) Viewed 342 times

[rheidtman]

The real key to getting the idle stop properly set is to ensure the throttle blade is perfectly centered. Failing this proper alignment, it will always be out of adjustment. Once satisfied is properly centered (I hold it up to the light to see how much light comes through and uniformity), I prefer to adjust 1/4 turn out from where the throttle blades to starts to bind internally. This provides just enough airgap to idle at a reasonable RPM, then using the idle screw to dial in.

[sefeing]

The real key to getting the idle stop properly set is to ensure the throttle blade is perfectly centered. Failing this proper alignment, it will always be out of adjustment. Once satisfied is properly centered (I hold it up to the light to see how much light comes through and uniformity), I prefer to adjust 1/4 turn out from where the throttle blades to starts to bind internally. This provides just enough airgap to idle at a reasonable RPM, then using the idle screw to dial in.

mmm interesting, i hadn’t thought about the tolerance on the plate itself. i’ll have to re check it before it goes in the car.

1/4 turn makes sense, but the S doesn’t have that idle screw, so i’m trying my hardest to not have to pull the intake again to adjust the TPS, if the mechanical screw also needs adjustment

that said, i did already blue loctite the screws in place for the plate…

[walfreyydo]

Do what you can to get the screw adjustment close, as mentioned by others, slightly open, but final adjustment will need to be done while the car is running. Proceed with setting the screw to have the TB slightly open, install on the car and adjust from there until it is approximately 900 rpm.

Clarks says the S and S2 do not have idle adjustment (idle is handled by the ICV) but your photo, which does appear to be a 16V S throttle body, does have an idle adjustment screw, so I think Clarks may have wrong information. FWIW, my S2 does not have an idle adjustment screw and its wholly controlled by the ICV.

[sefeing]

Do what you can to get the screw adjustment close, as mentioned by others, slightly open, but final adjustment will need to be done while the car is running. Proceed with setting the screw to have the TB slightly open, install on the car and adjust from there until it is approximately 900 rpm.

Clarks says the S and S2 do not have idle adjustment (idle is handled by the ICV) but your photo, which does appear to be a 16V S throttle body, does have an idle adjustment screw, so I think Clarks may have wrong information. FWIW, my S2 does not have an idle adjustment screw and its wholly controlled by the ICV.

i can confirm there is no screw on the S - the place that LOOKS like it has a screw (the TB is similar to the Turbo’s) is blocked off / not drilled out, so no adjustment to be made. The (expensive) IAC is a variable one, the same off the 964.

[walfreyydo]

Do what you can to get the screw adjustment close, as mentioned by others, slightly open, but final adjustment will need to be done while the car is running. Proceed with setting the screw to have the TB slightly open, install on the car and adjust from there until it is approximately 900 rpm.

Clarks says the S and S2 do not have idle adjustment (idle is handled by the ICV) but your photo, which does appear to be a 16V S throttle body, does have an idle adjustment screw, so I think Clarks may have wrong information. FWIW, my S2 does not have an idle adjustment screw and its wholly controlled by the ICV.

i can confirm there is no screw on the S - the place that LOOKS like it has a screw (the TB is similar to the Turbo’s) is blocked off / not drilled out, so no adjustment to be made. The (expensive) IAC is a variable one, the same off the 964.

That bolt you point to in the photo must be used to adjust the butterfly completely closed position. I was pretty sure the ICV controlled idle speed on all 16V cars but the S sometimes can be slightly different from the S2s, and the throttle body on my S2 doesnt have any adjustment bolt anywhere..

Your best bet is to adjust that bolt to where it most completely closes the throttle (without it sticking) and then install, fire up the car and see how it idles. If idle too high, just adjust the bolt a bit and have the throttle close more. If that doesnt work, try cleaning out the ICV in case there is some gunk/buildup that doesnt allow it to fully close/open.

You may also want to review the factory service manual and determine if there is a factory process for setting that bolt correctly. These are freely available for download here:
http://p914-6info.net/944%20Manuals.html

[sefeing]

Do what you can to get the screw adjustment close, as mentioned by others, slightly open, but final adjustment will need to be done while the car is running. Proceed with setting the screw to have the TB slightly open, install on the car and adjust from there until it is approximately 900 rpm.

Clarks says the S and S2 do not have idle adjustment (idle is handled by the ICV) but your photo, which does appear to be a 16V S throttle body, does have an idle adjustment screw, so I think Clarks may have wrong information. FWIW, my S2 does not have an idle adjustment screw and its wholly controlled by the ICV.

i can confirm there is no screw on the S - the place that LOOKS like it has a screw (the TB is similar to the Turbo’s) is blocked off / not drilled out, so no adjustment to be made. The (expensive) IAC is a variable one, the same off the 964.

That bolt you point to in the photo must be used to adjust the butterfly completely closed position. I was pretty sure the ICV controlled idle speed on all 16V cars but the S sometimes can be slightly different from the S2s, and the throttle body on my S2 doesnt have any adjustment bolt anywhere..

Your best bet is to adjust that bolt to where it most completely closes the throttle (without it sticking) and then install, fire up the car and see how it idles. If idle too low or too high, try adjusting the bolt a bit and see if it changes anything until it is dialed in at your target RPM.

You may also want to review the factory service manual and determine what the factory process is for setting that bolt correctly. These are freely available for download here:
http://p914-6info.net/944%20Manuals.html

Yep! I can't for the life of me find it in the service manual. Correct- that bolt is a manual throttle plate stop. The ICV does control idle speed on the S - the only issue with adjusting this on the car, is that the TPS must also be adjusted, which requires pulling the intake on the S to adjust. The S2, base and turbo are much easier to access

Going to do another read thru the service manuals to see if I can find