High idle drama....endless

Starting a new thread, hoping I develop a new level of enthusiasm for solving this problem.. '99 C2, 100k miles. I have an idle that started sticking at about 1200, then progressed to 2200 rpm. 1) First step was to check the air idle control valve. As you can see from the picture, it had a crack with a corresponding tear in the gasket. Replaced, no improvement. 2) Opened the junction case where the two cables connect under the car. Cleaned thoroughly, looked good, no improvement. 3) Cleaned throttle body. no dice. 4) Compounded my problem by disassembling the throttle pedal, Cleaned and lightly lubed. Upon reassembly, now find my throttle cable too short by approximately 3/16" (see photo.) Followed previous advice with pulling rear cable to seat plastic grommet at throttle body, opened junction onder the car and made certain both cables were not binding, fiddled and diddled, but the cable too short. a) Is it possible I somehow shortened cable inadvertently inside the throttle with reassembly? IS the thumbscrew looking piece on the cable junction case an adjustment for cable length? (See photo) So I must first solve the cable issue, and then address a possible vacuum leak for the original problem of the high idle. All constructive suggestions are eagerly encouraged!

pull the carpet back at the base of the throttle pedal. There is a little sheath on the cable that can get caught on the plastic piece where it enters the pedal assembly, which would cause the issue in question.

Thanks Quadcammer - took a look, seems to be seated properly, though under tension very difficult to see, release tension and then isn't seated...

that mechanical pedal is quite a maze. double check that, but be careful with the pin at the bottom, its a bit fragile

Just a thought...undo the cable from the TB. Does the throttle plate and return spring hit the post? If yes, the throttle cable is binding somewhere. If not, something is wrong with the TB. Leave the cable detached from the TB and start the car. How does it idle then?

Here is mine and you can see there is no gap between the plastic thing and the post

The idea of reopening the throttle pedal box is nightmarish. I presume that any slack in the cable that may have been in the box would be gone as soon as tension was put on it. There is no feeling of cable binding either in the first piece or piece to engine. DBJoe - the throttle plate hits the post no problem without the cable connected. Need to find 3/16"s of cable hung up somewhere. But even when the thing hit the post (before my disassembly of throttle pedal) the motor was sticking at 2200 rpm. My next job was to search for a vacuum leak. But first, the cable......

Agree...you need to find out where the cable is hung up first. I forget the original reason you were in there. Is it possible the throttle cable is misrouted across the top of the engine? I would still give that cable a really good tug after you check out the other cable connections.

Diagram of accelerator pedal and cables. It really is pretty simple. http://www.autoatlanta.com/porsche-p...section=702-10

Quotes source post: 16819845

In this diagram, and also in the original post's top picture is a device called a "housing". Many times on cable actuated systems there is a slack adjuster inside these things - a ratchet to shorten the cable to fit the exact setup. You usually can shorten the cable but not lengthen it. The cable operated clutches on older VW's use this kind of a ratchet, and now that I think about it the throttle cables do as well. Could this be the reason why your cable is too short? The cable got shortened by the slack adjuster, if that's what it is? I do not have a DBC mechanical throttle 996 handy to look at, my car is e-gas equipped.

When I experienced this identical issue, high idle because throttle cable was too short, the problem turned out to be the throttle cable sheath's metal tip. You mentioned pulling on the throttle cable to ensure the plastic grommet was properly seated in the throttle body. My problem turned out to be that the metal tip of the throttle cable sheath had separated from the sheath and had the effect of making the sheath longer and the throttle cable shorter. Once I realized what was going on, after having pretty much followed the identical diagnosis you did, I simply jammed the metal tip back onto the sheath at the throttle body end and ensure the throttle sheath/tip were well seated in the throttle body plastic grommet when I pulled the cable through. Voila, no more gap at the throttle body stop post and the high idle was resolved. You may want to ensure that the metal tip at both ends of your throttle cable sheath are firmly seated on the sheath, my issue happened to be at the throttle body, but I could imagine the same issue might impact the gas pedal end as well. Try the throttle body end first, its easier. Best of luck.

In this diagram, and also in the original post's top picture is a device called a "housing". Many times on cable actuated systems there is a slack adjuster inside these things - a ratchet to shorten the cable to fit the exact setup. You usually can shorten the cable but not lengthen it. The cable operated clutches on older VW's use this kind of a ratchet, and now that I think about it the throttle cables do as well. I wouldn't doubt that I screwed this up. Operating in the wheel well of my car in 90 degree heat, not a recipe for success. As for Weazer's point; I did find the metal tip had separated from the cable sheath. But even after sorting that out, cable was too short. I have thrown in the towel on this one. Spoke to my independent - he thinks the intermittently "stuck" thropttle may have something to do with the cruse control. I do use it a lot. Sticking seems so arbitrary, unrelated to engine temperature, doesn't respond to my stabbing the gas to try to get it to settle. When the throttle sticks I am forced to leave the car in gear and brake down to 1000 rpm before depressing the clutch. Car then returns to 800 steady idle.

Just looking for a new cable from gas pedal to box connecting to rear cable.....don't see a part number on it. I will flip my wig if that means I have to buy the whole pedal assembly

Quotes source post: 16820938

google, looks like $60 https://www.porscheatlantaperimeterp...642322904.html

I would disconnect the cable from the throttle body and start the car and check the idle. If it still idles high, the cable is not the cause or at least root cause. Air leaks most often cause a high idle. You need to rule that out first.