I think you can do the same with propane. introduce the propane to the area where you want to check for a leak. The leak will suck it in and the idle should change.

Or you can just take a weekend to replace all your vac hoses:)

Took me about 2 hours to do my vacuum lines. The hardest ones to reach are the ones that connect to the firewall behind the engine. My idle is still very low in cold weather though, which is why I think either my ISV is bad or the signal isn't being sent to it properly. I tested it with a 9V battery and it opens and closes quickly with a signal.

Clamp the vac hose from the manifold to the ISV. If the idle smooths out, most likely your ISV is bad or dirty.

Which line are you referring to? There aren't any that go directly to the ISV.

http://www.clarks-garage.com/graphic...uum-line-1.jpg

Anyone know where an early model/ 924S vacuume line diagram is? I think Ive seen one before, but have no idea where, or if it was on Rennlist.

I dont know if the ISV is same or different for the NA and a 951 but it's the big black hose thats connected to the manifold between cyl1 and cyl2. Check the pic.
http://forums.pelicanparts.com/uploa...1259708362.jpg

Here's my own pic:

http://www.theexitwound.com/944/icv5.jpg

The one shown connected to the ISV goes to the J-boot and the one not shown (removed) goes to the intake manifold. You're suggesting clamping off the hose that goes to INTO The ISV (the one shown), correct?

How does this trigger the car's idle to change?? I've never fully understood this ISV system.

The hose going to(or coming from I dont know which) the manifold has to be clamped as per clarks garage.

Troubleshooting - Engine

Well, i dont have a surging idle. It's very stable at 500rpm when the weather is cold. I don't have a garage, so the car sits out in the cold air all night. When it warms up, after a few minutes, it idles around 1000-1100.

500rpm? My car isnt even stable at 950 lol. Ok, well atleast you know how to check the ISV:)

Yeah it's stable. And by that, I mean it's a rough stable. The engine can run at 500rpm, but I'll tell you, it shakes like San Francisco. The headlights are up on my car (my decision for clearance sakes) and they rattle like nuts. The hood hops up and down enough to make noise. There's something in the dashboard which is rattling, something in the door, the engine can literally be seen shaking. My guess is that it's not designed to dampen a 500rpm idle. So I keep my foot on the gas for 30 seconds or so to keep the idle at ~1000 and it tends to be okay after that. I'll have to get to checking that ISV again when I have a weekend.

Just did the FR Wilk throttle stop adjustment last night and got rid of a horribly loping idle. At the end I set the RPM to 1000 via the stock tach. Running very smooth and was pretty much out of adjustment on the air flow screw anyway.
BTW - I'm a big fan of the propane method for vacuum leaks over any spray can product. A lot cleaner, safer and I think it works better. Really helped my find a vacuum leak on my motorcycle earlier this year.

LOL. That doesnt sound stable to me. Maybe you mean stable is in your car doesnt stall? I was under the impression that the idel is suppose to be a bit higher when cold and then drops to about 950 when warm. Not 500. 500 is barely running. Thats why the car is doing that. My car does that. Hate it. When your car is warm how smooth is the idle at 950rpm? If it isnt smooth humming away. I would check the ISV. Checking the ISV is very easy. Takes two seconds. When I clamped mine off I could not believe how much smoother the idle was. Theres also a diagnostic plug too. Where you can disable the ISV.

Yeah I had to set my idle a bit high to smooth out my idle. You should put a bit of silicone on the top of the idle screw to keep it from backing out. I heard the propane method works great. I will have to try it out.

When warm, the idle at 1000-1100 is perfect. No lapping, no movement, no threatening to stall, no indication that there's anything wrong. Even at 500rpm, there's no movement, it's just extremely low...no threat to stall other than running too low.

And I've bypassed the ISV electronically via the diagnostic port to set the idle higher. Can't change the idle on the late 944 without doing that. There's no immediate change when I jump the ports. Should there be?

But how does your car idle at 950rpm? My car idles fine between 1000 - 1100 too. Thats why I upped the idle to that range. At 950rpm my car drops low and then jumps up high. Very random. You should disable your SIV again and set the idle to 950. See if the car idles nice at 950. Is your car chipped? If your car is chipped it might not idle as nicely at 950 because the chip is changing the fuel map. It might idle nicer. I dont know. but see what it does at 950.

If I remember correctly,... I dont remember anything noticable when I disabled my ISV either. I remember questioning whether or not the ISV is truly disabled by jumping the ports. When I clamped the hose,... big difference. Idle smoothed out beautifully. Almost left it clamped:)

It idles perfectly no matter where I set the idle. From 800 to 1100 it's steady. no fumbling, lapping, rocking, nothing. needle is steady. Engine purrs. Even at 500 it's steady. Just really really low.

950 if the AFM is not acting up 1200 if it is

Mine changed! It was idling at 1K-1.2K higher with fans. Now I screwed with the idle adjuster im at the 850-975RPM range while at idle. This is what was heppening before. The pictures are he worst spit its done. http://forums.pelicanparts.com/porsche-924-944-968-technical-forum/515019-condensation-tailpipe-oil-cap.html