Do I need my Thermo Valve?

[Hulley]

1979 SC with original CIS, car is stock except for SSI exhaust.

I'm chasing an idle issue that cropped up in the last couple weeks and in doing so, I have noticed that the vacuum line going from the Thermo valve to the WUR was not even hooked up. I've owned the car for over a year and seem to remember it never being hooked up and car has always ran great, until recently.
I got this pic from Jim's Basement and it looks like the Thermo valve only activates for 20-30 seconds upon start up, if that's the case, it shouldn't cause my idle issue, right?

Can't I just run a vacuum line from the "T" straight to the WUR? I understand cold start might be affected some but that's only for a minute or so.

I'm having difficulty finding a Thermo valve, they seem to be NLA.

[Schulisco]

The best way to get support is that either you describe exactly what the engine does or you better make a video and put it online that we can see what's going on. Every part of the CIS can have a negative effect and it's far easier to help you out with a video.

Concerning the thermo valve you'll find here at the forum more information. E.g.
https://forums.pelicanparts.com/porsche-911-technical-forum/267143-thermo-valve.html

Thomas

[boyt911sc]

Take a look.

https://forums.pelicanparts.com/porsche-911-technical-forum/775313-ttv-test-results.html

Tony

[Hulley]

Originally Posted by boyt911sc

Take a look.

https://forums.pelicanparts.com/porsche-911-technical-forum/775313-ttv-test-results.html

Tony

Thank you, that pretty much answers my question. I was able to order a new part from my local Porsche dealer and will have it by the weekend, however I don't think it'll fix my idle issue. I'm going to go ahead and replace the thermo valve just to remove it from the equation as it wasn't too expensive ($132.00).

[boyt911sc]

Hulley,

You probably misunderstood the function of the TTV. It is off or closed for the first 20 sec. or so for a cold motor and remains open up to the time you switched off the motor. Without one, your control fuel pressure would be too RICH to cause erratic idle.

Tony

[Hulley]

Originally Posted by boyt911sc

Hulley,

You probably misunderstood the function of the TTV. It is off or closed for the first 20 sec. or so for a cold motor and remains open up to the time you switched off the motor. Without one, your control fuel pressure would be too RICH to cause erratic idle.

Tony

I understand. In my OP I stated that I was chasing an idle issue that just cropped up, also that the vacuum line from the TTV to the WUR has never been hooked up, so if it has never been hooked up then it's probably not the cause of my idle issue. I was asking if I could bypass the TTV with a vacuum hose going directly from the decel valve to the WUR while I continue to chase my idle problem.

Seeing as I was able to locate a TTV, I went ahead and ordered one so at least that will be a non-issue and I'll still have to diagnose my idle problem.