Idle Speed Question
 

Well, I'm at about 500 miles since I got the motor back in my '83 930. I've done many searches and spent a lot of time reading through past threads about Decel Valves and AARs (pardon my ignorance if I missed anything), but can't seem to come up with a plan of action.

Scenario:
- Cold Idle - 600 RPM
- Warm Idle - 600 RPM
- Hot Idle - 1400 RPM
- Hard to make it Warm Idle at 900 RPM, it either wants to be at 600 or 1200

I'm going to check to make sure that the linkage has enough slack and has room to "expand" without cracking open the throttle plate when hot. If that isn't the problem, what else could it be?

Thanks!

Could be a bunch of things - including if your WUR operating correctly . Plus maybe an air leak. A rich mixture and a small airleak would do that sort of stuff.
Check also the AAR is operating properly. Basically probably a matter of systematically working thru stuff eliminating possibilities. Maybe timing would do it too.
Alan

I had some strange idle issues like this happening shortly after I got my AAR installed and working, it was previously uninstalled by a PO who said it didn't work properly. I fiddled with some things and switched the WUR and AAR connectors (they are physically the same) and its functioned properly ever since. Maybe a fluke, maybe not. If you had your motor out, perhaps you plugged these connectors in wrong?

I forgot to mention that, I installed a BL adjustable WUR and adjusted it to spec (will verify pressures again). Timing is adjusted to spec.

How is AAR troubleshooting done? Could the Decel Valve have any effect on this?

I think you have the vacuum lines from the dizzy connected wrong, try flipping them, so what may be happening is that you may be getting vacuum at cold start and retarding the timing , bringing you idle down, then when the engine is warm the thermo valve closes and and now you get advanced timing which bringing up you idle, you want it the other way around, try flipping the hoses on the T/body , their should be one on top and bottom. take pics

here's how to test it, when the car is cold, unplug the two vacuum hoses, the rpm's should raise

cold start should be 1200 to 1400 then drop in about three minutes
warm and hot should be the same 950 to 1100

I thought I had an issue with my vacuum system/AAR, but after a couple of runs where it idled around 2K, the issue has disappeared, and everything is in the 900-1100 range. At this point, I'm willing to let it go until something changes, and write it off as something that happened during reassembly that just had to work itself out. Unless it comes back, that's all I'm left with.

Good luck!

just to make sure, the idle is adjusted with the big screw that goes into the side of the TB.

i dont know if your car has the throttle switch on the side but make sure it is adjusted properly. mine is not used and it was on the edge of making it idle at different settings.

vacuum line routing to the dist as mentioned.
if it is switched, the vacuum retard is run thru the thermo time valve then to the vac advance pot, it would raise the idle once it warms up.

i dont agree with how porsche did this. here is how and why i ran mine
i ran the vacuum retard to the themo time valve then to the retard pot.
porsche ran the vac advance to the thermo tinme valve (TTV). they did this so the advance would not kick in until the engine warms up. problem with this is if you go on boost when it is cold, there is not boost retard which i think is worse.
running it the way i did ups the idle a little more when cold.

- Tested the AAR by putting 12V to it and made sure the "flap" closed. It moved freely and closer 98% of the way, tiny gap at the very edge, is this normal?

- I understand that the part next to the AAR is the AAV, should that be checked? If so, how?

- Found a few hose clamps that weren't tightened, I'm sure this could have been part of the problem.

- Distributor hose routing, please confirm.
- Port facing AWAY from distributor body -> gooes to bottom of throttle body
- Port facing TOWARD distributor body -> goes to thermo valve, then the left side of the "T" on top of the throttle body

Image from http://forums.pelicanparts.com/uploads14/Dizzy+vacuum+11225194029.jpg.

For modified 930's , this is the setup I used ,
Image from http://forums.pelicanparts.com/uploads18/Schlauchschema13055527931306801622.jpg.

it,s important to keep that switch for the cold start, it will increas the the idle by 300 rpms at the cold start ,along with AAR , the switch will then close after 2min , The diagram from jcc911 is the way to go just keep the switch. as for your timing it depends on what dist you have , get the number that is stamped on the side , that will tell you what the spec for your dist, and also whats the max octian in your area , and what boost , do you have an after market intercooler

Yes, normal. It's never completely closed (it's got a weird cross-shaped opening, more or less will be exposed).

i would call hello.... i had the exact same problem, porsche could not figure it out,, all the manuals said they had it correct but helio proved them wrong..

Looks like flipping the hoses to the distributor (heliolps2, thanks!) did the trick (I'm sure snugging all the hose clamps helped as well). Idle smoothed out a whole lot and the idle air screw responds as it should. Idle speed is now a solid 850rpm and didn't fluctuate as the engine warmed up.

As for the thermo valve, I will check and see how it starts tomorrow when the engine is cold.

Great .. Glad that I could help,

Hey john, I hope all is well, I had forgotten about , Porsche of Scottsdale, they were amazed how that worked .. I had way to much time on my hands, to figure that out . Now I miss my yellow beast, the 993 isn't the same .. Lol

number 9 that was removed is there to prevent boost from hitting the retard port on the dist. if boost is on the retard port AND boost is on the advance port (the advance port is the one that retards the timing when on boost), then the timing does NOT retard.

what i am telling yours based on the 86, not sure of your year.

the port facing away from the dist is the advance/boost retard port.
the port facing the dist is the idle retard port.

i think your vacuum lines are still messed up even after swtiching them.

remove the TTV from the advance side and put it on the retard side. it will raise the idle when cold. run the vacuum advance directly to the TB.

How did the cold start work out ?