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High idle help needed on 1983 911SC 2000 rpms

jumpinjimmy

By jumpinjimmy
in 911, 912 Series

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jumpinjimmy Member

jumpinjimmy

Posted
Posted

Hi, I've just bought a 911sc cabriolet with a problem of high idle when hot.  The car starts easily, idles roughly at 900 rpms and then as I drive for a while it settles in to a 2000 rpm idle that won't go away.  If I stop the car for a short period of time and restart, the idle once again stumbles at 900 and then starts to creep up to 2000.

 

From what I've read on forums, there seems to be so many different places to start troubleshooting...any suggestions?  acccumulator?  WUR? simply adjust idle and fuel mixture?? crack in airbox?  vacuum leak??  

 

Any pushes in the right direction would be appreciated.  The car has a very complete service history and I see where the WUR was changed with a second hand unit at one time and then a new unit replaced that one a few years later.  When I received the car, I also noticed one of the electric plugs to the WUR, the one towards the back of the car, had been disconnected.   I reconnected it.

 

Thanks in advance.

 

Steve

 

here's a pic of the car.

 

 

post-62174-0-66213100-1416346646_thumb.p

  • Admin
Loren Member

Loren

Posted
  • Admin
Posted

If course an air leak is possible - there are lots of hose and fitting (and the car is 30 plus years old). But, I would also check the cold start valve to see if it is leaking fuel after warm-up. That was a fairly common problem on these cars.

 

Next after those would be fuel pressure and the fuel pump. Any starvation at high RPMs? If so, it could be a weak fuel pump or bad pressure regulator.

Uwon Member

Uwon

Posted
Posted

Tap the idle control valve several times with the plastic end of a screw driver. If the rpm lowers, you are on to it. Next would be vacuum leak. There are several threads on this in the Pelican 911 Technical forum.

Good luck.

Johan

Uwon Member

Uwon

Posted
Posted

Hi Steve,

I think that I have mislead you for which I appologize. You have the K-jetronic FI system rather than the later system that I'm more familiar with. As such I don't think that you have what I referred to as an idle control valve.

In looking at the PET (http://www.porsche.com/usa/accessoriesandservices/classic/genuineparts/originalpartscatalogue/) illustration 107-10 and 107-20, you have an air by- pass and warm up valves that may be the problem(s). Aside from that, a post on Pelican, will undoubtedly provide you with some beneficial responses.

Good luck.

Johan

  • 3 weeks later...

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