Medski

Ddi it do something like this: (this is mine btw) I haven't touched the gas pedal the whole time, and the engine was warmed up. (Cold it idles at 1k, until is gets warm then see vid....) And goes back and forth like that...


I haven't traced what is causing this yet. And now the car is storaged for the winter. You guys also lost me with the ICV and ISV lingo. What acronym is that?

xsboost90

sooooo never verified a vac leak? sounds like the easiest thing to check and fix but somehow we assumed that its not. Also- ever disconnect the cruise cable?

Medski

Nope, the whole ''car almost getting stolen and broken windows episode'' kinda delayed that. I haven't tought about the cruise cable though... Gonna note that. But since the car is storaged now I can't work on it. So i'm just looking at possible issues and clues to 1) pass the time and 2) get some reading done.

bonus12

Well, after getting the idle to 900 by twisting the idle screw all the way in, I drove 100 miles. The car ran really well; it was very consistent and powerful, and it sounded fine.

How can I be sure I'm not running too rich or lean? I'm a little concerned because I had to tighten the screw all they way in and I may be masking another problem...not sure if I am or not. Is this screw supposed to be all the way in...can this be normal?

Debra 785

Any thoughts? When I got the car about a year ago, it idled fine.

mytrplseven

I still recommed checking the vacuum system for leaks. I took my intake system totally apart and even though I thought I found all the possibilities, There was another one under the J boot. A small theree-legged T fitting was previously broken by some hand-fisted mechanic and glued. It came apart in pieces. But that notwithstanding, go to a hardwarde store, get a properly sized (2" for NA car and not sure about a turbo) and thread an air fitting into it and pressurize it to 7 to 10 psi and spray everything with soapy water solution. Look for bubbles. It's easy and you'll know once and for all if vacuum is the issue. Get a copy of the vacuum system from Clark's garage and trace down every line so you'll know you've covered it all. Oh, and don't forget: check the throttle body, too.

bonus12

I'm going to do this vacuum leak test. Any recommendations for machines to pressurize air?

Justin S2

Weird. My S2 just started to do the same thing once it started being colder out. I'll have to investigate in mid december to find out whats wrong.

One somewhat stupid question is could it involve the AFM? I know a lot about 944s, I'm just not sure what the symptoms of a faulty AFM are.

alan t

I guess the cold can start cracking the 20+ year old vacuum lines and idle stability valve hoses. When my idle started fluctuating and going bonkers, I took the manifold off and found major cracks all around the small S-shaped ISV hose. You could even see light through the hose, and there were a few in this same condition. There's no way of seeing this and some other lines/hoses without taking the manifold off. At least on my 85 NA. It's got to be less expensive to start replacng the hoses than starting to replace ISV or TPS.

friendlyguy64

SOLUTION SOLVED....

ok guys so I have an 88 951!!! I just had the head replaced, all the vacuum lines, dme temp sensor, removed the ICV and yet I still got the high idle staying around 2k rpms. Next step was to check the TPS. So I checked the voltage like Clarks garage suggested it, everything seemed fine. So I decided to take a closer look into the TPS sensor. When I opened it up nothing but oil came out of it!!!! I knew my turbo was leaking oil, but not this bad!!!

So guys before you go out and spend your money on vacuum lines, ICV, etc open your TPS and see if theres oil!!! The oil dried up so that when the throttle moved the strips would stick!!!


How this helps out everyone....Its been months for me....

JustinL

This is one of those problems that you need to think logically about. High idle means there is more air entering the cylinders than there should be. Work backwards from there. Intake manifold gaskets, vacuum lines, brake booster line, Idle control valve, throttle, throttle bypass screw. Start checking these and it will reveal the problem 95% of the time. If you can get the manifold pressure (vacuum) it makes it really easy to solve.

xsbank

Buy a silicone vacuum line kit (cheap and excellent value) and replace all your lines - takes about an hour, makes leaks go away and adds a groovy colour to your engine too! Start there.

F18Rep

I got lost in this thread, yes the turbo TPS fill up with oil, there s fix for that. But the title says its not a TPS, so just a shot in the dark but I would pull the vacuum line off of the FPR and put a vacuum gun on there to see if there is a pin hole in the FPR's diaphram. A pin hole, would allow fuel to get sucked into the intake and alter the mixture/idle ... same effect as a choke on your mini-bike.... do they even make mini-bikes anymore? Signed... the geezer

rjai0972

Recent graduate from automotive tech. i believe that idle screw is set there by manufacture and you should not move it works as a bypass to allow oxygen to get into the intake manifold to allow smooth idle i do not believe that screw was your problem. my engine performance instructor told me when screw is moved it is very hard to get back to its proper setting and you will probably have to replace the throttle

peanut

exactly right my friend ! but folks will fiddle and adjust things at random when desperate
Commensense should tell anyone that the idle screw couldn't back out by itself so couldn't be the cause of the problem. Screwing it in might give a tempoary fix but its simply disguising the source of the problem.

Well done on graduating and welcome to the forum .