idle hunt

[Porsche-poor]

Drove the car about 6 hours from home. Tacoma to Bend. Car drove like a champ till I got here and shut her off. Then she would not start and run. Finally got her to start and stay running but the idle was way low so I dialed it back up. Now sitting at lights the engine goes up and down about 100 rpm. Its a lot hotter here than we are used to. Once I get home any thoughts on where to start to fix this issue? It is a 79 sc.

[Paulporsche]

When it's suddenly hotter out, sometimes a mixture that was right for cooler temps becomes too rich. A hunting idle is a very common symptom of a too rich mixture. You have to tell us more. Has the mixture ben set using an analyzer? What CO%. Have you checked your control pressures? (WUR). Shutting the car down and then not restarting (how long after?) could mean warm control pressures off or fuel pump check valve, or even likelier, the fuel accumulator. I suppose it could also be a leaky cold start valve or even a bad CDI box, but I'd look into the above things first.

[Porsche-poor]

would not run at all after checking in at the hotel unless you kept you foot in the pedal. got her parked and left it overnight, she started fine and got thru the first few stop lights but would then die when you put in the clutch. I pulled into a lot and got the idle up so it would run. When I get home I'll start in on the list you gave me. Does a 79 3.0 liter have a CDI box?

Thanks

[Paulporsche]

Yes it does.

Are you familiar with, or have you searched how to check your control pressures? You want to make sure your fuel pressure, cold and warm control pressures are right, and your residual pressure is correct.

It's also wise to always make sure your ignition system is working correctly and you have no vacuum leaks.

[Porsche-poor]

I got back over the pass and had to dial down the idle speed. I am wondering if it was just an altitude issue. The car is used ot being at about 500' and was at 3500'

[Techne]

Mine isn't an SC, but it was also hunting at idle in this heat - 98 on Saturday. Maybe that is the reason for both of our woes?

[Vincent Hill]

I never leave home without a long 3 MM Allen Wrench! I have never seen 1 tool that could cure more CSI Ills symptons! You may have other problems that cause what is going on but the 3 MM will make it run rught until you get back home!

WIth the top of the "L" end facing you remember left is lean and Right is Rich! Usually they are rich when the are trying to stall and low RPMS. High RPMS is usually lean and in my case was air leaks but with that wrench I tuned them out until the parts I ordered are delivered!

[Joe Bob]

Sounds like an intake leak....

[Porsche-poor]

I finally got around to warming the car back up and dialing the idle back down to the correct setting. No more hunting idle steady as a rock. Thoughts at this point? There is a about a 3000' elevation difference between home and where I went. Could that have caused the issue?