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S2 Idling Fault

Re: idling fault " hunting ". had the same problem with a '90 S2 @ 60K miles -- most journeys local at the moment - surmised that the car was protesting at not being extended. A dose of somebody or other's injector cleaner in the tank and a dual carriage way blast for a few miles has sorted it !

P.S. Porsche World Oct. issue 944 owner complains about the worrying "whistling" from the region of the timing belts. Had the same problem -- expert advice suggested timing belts too tight -- had them inspected by indy Porsche specialist who agreed and eliminated the problem.
 
Driving through town yesterday i pulled up to the traffic lights and the rpm went up to 1300 at idle and missfired a little when i touched the pedal.It did it 2 or 3 times during the journey so i decided to have another go at the ISV.
I've had look at the ISV this morning but there was no way i could get at it to comfortably disconnect both hoses.
Anyway, i disconnected the hose which fits onto the large plastic hose fitted to the air flow sensor which leads into the base of the ISV.
I liberally sprayed carb cleaner down it and to be fair there was a lot of oily residue present.I connected it back up and started the ignition.She fired up but seemed to struggle for a short time which cleared.
Took her for a short spin and although she drove ok when i pulled up the revs again went up over 1200 then dropped just under 1000rpm and seemed to settle at that.Will it take time for any residue to clear through the ISV or should i have another go followed by a long "spirited" run?
 
It isn't unusual to run a bit rough when you first start it up (it draws carb cleaner rather than the air it expects) but after that it won't get any better. When I did mine off the car it took a good bit of cleaner and cleaning to get it shiney. If it isn't shiney then it has a coating of varnish on it.
 
I've never done that. I think the problem with them is the electrical contact track gets druty/worn but it's easy to damage them bu opneing them up.[FONT=verdana,geneva"] [FONT=verdana,geneva"]You can clean the flap and also the throttle butterfly but they have much less bearing on idle than the ISV.[FONT=verdana,geneva"]
 
Disconnected the hose again today and sprayed more carb cleaner inside.Seemed to run smoother to be fair.Does sound like it's ticking over better.
I'm going to adjust the throttle cable tomorrow as there seems to be quite a bit of slack in it.I assume it should be fairly "taught" whereas mine can be moved easily by where it connects up by the inlet manifold.
 
I guess if it's really slack you could have a problem but really it needs only to be loose enough that the throttle butterfly closes all the way (you should hear a click when it does). Too loose and you won't be getting full throttle when you floor it!
 
In that case then i'd say it's very loose - where the cable is exposed you can pull it with ease left to right a good inch or so.I'll try and take up the slack with the adjuster.Is it possible the cable could be stretched?
 
ORIGINAL: 944cabby

In that case then i'd say it's very loose - where the cable is exposed you can pull it with ease left to right a good inch or so.I'll try and take up the slack with the adjuster.Is it possible the cable could be stretched?
Click to expand...
Here's a pic of the end of the throttle cable to show the amount of slack in it.I'm holding the inner cable moving it towards the right but not forcing it at all.Does this seem more than anyone else's (or am i being paranoid)?
http://img367.imageshack.us/img367/3840/cable4ap.jpg
 
if you've got loads of play in the throttle cable, then it can't be affecting the idle. It would just mean you had to press the "go" pedal a bit further to operate the throttle. As soon as you let off, the throtle body/springs will just do their thing. If the cable was tight, that would be another thing.....

is the throttle butterfly sticking at all? just rotate it by hand, and let it go. after tht, try to push it closed. if it does actually need pushing closed, then you have an issue, although it could be numerous little things: too weak a spring, stuck o-rings, worn shaft etc etc. if not, I would suggest either the ISV is to blame, or you may even have a major vacuum leak. (although i need to think about that last one a bit more!)

 
I agree with Mike. That cable slack looks OK to me in any case.[FONT=verdana,geneva"] [FONT=verdana,geneva"]I really think it's the ISV. I can't remember how I got mine off and I don't have an S2 handy to jog my memory but I did get it off and it took a good bit of cleaning. It won't do any harm to clean it on the car but if you get it off you'll be surprised at the crap still in there and it will take a good 5 minutes of spraying and working it to get it shiny. [FONT=verdana,geneva"]
 
ORIGINAL: Fen

I guess if it's really slack you could have a problem but really it needs only to be loose enough that the throttle butterfly closes all the way (you should hear a click when it does). Too loose and you won't be getting full throttle when you floor it!
Click to expand...

A bit of slack on closed throttle isn't a problem. The thing to check is that with the pedal floored, the throttle is opened all the way. If it isn't you'll want to adjust the cable. If it is, just leave it alone. You shouldn't have the cable tight, because that will stop the throttle closing completely and you'll get idling problems.
 
Did you get round to trying out the suggested fix Phil?

This all sounds very similar to a problem that I have had very intermittently over the past several years. For me what happens is that when warm, the engine ticks over nicely at 900 odd rpm. If the throttle is blipped, the revs "undershoot", dropping almost to a stall and then recovering to normal tickover. On one particular day, the engine was also very hard to start from warm and when it did start, fired on about one cylinder for several seconds. This happened every time I started from hot that day but has never happened since.

Does this sound like the same problem that you have had? I'd be really pleased to hear if you manage a definitive fix this problem.
 
On my 'S' the elevated idle was the ISV. The drop off and bounce back up was the AFM. I have pulled the cover off my AFM and fixed it by moving the arm down the spindle so the arm rubs in a new arc. Work perfectly. I had top remove my manifold to get at my ISV. Due to that I wasn't going to chance it and just clean it as yanking the whole lot off again was more than I could face.

See here for details http://www.porscheclubgbforum.com/tm.asp?m=111344&mpage=1&key=AFM𛧒 there is a link which takes you to a website on the AFM

 
I didn't get round to trying the fix as the next time I drove it, and I was specifically looking for this problem, it didn't happen. The engine was then removed - I did suggest to Peter that the ISV was checked and judging from the picture of the engine Peter posted on the "Rust on a 944" thread I'd say the ISV was off the engine now, along with the inlet manifold, timing belt, balance belts and pretty much anything else that could be removed!

Phil

 
One thind that Dave noticed whilst disembowelling the engine was that on some of the connectors the protective coating Porsche put over them had melted which could have made poor connections, particularly if they were distrubed. They looked like they'd be a real swine to clean up and so were replaced.
Apparently this is a more common problem on the 928's due to the higher temperatures the connectors are exposed to, but quite rare on 944's.
Whilst he was in there he also cleaned the ISV too, so between the two hopefully it should solve the problem.

Best regards,
Peter.
 
Thanks for that link. I'm going to give it a go to see if I can breath a bit more life into my AFM. Hopefully it'll cure my car's current case of asthma [:-]
 
It is a good fix and has been running fine for the last 15 000 miles on mine. I would just heed the warnings about fiddling with other settings in the AFM. I didn't even clean mine for fear of nudging something critical.
 
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