'83 911SC High Idle (in cold?)

HDBrown · 02-08-2007, 04:48 PM

I have owned this '83SC for 5 days now. When I bought it, it idled at just over 2k rpm for about 15 minutes before it idled down to just under 1k. I drove it tonight (26deg F outside) for about 20 minutes and it never idled down, it wanted to idle at 2300 rpm. Ideas?

VaSteve · 02-08-2007, 05:19 PM

Your sig indicates an 81....did it work the same?

Mine revs up real high when the engine is cold and then hunts for a bit until it's warmed up. Did you drive it or was it sitting in the driveway idling like that?

It's really cold so that might be a factor...I'd look for sticking accelerator linkage, bad WURs and such. But I think you need a few more days to gather more data.

HDBrown · 02-08-2007, 06:00 PM

Yes, I did drive it for 20+ min and I do need a few more days to gather data.... like "what year is the car I bought?" ha ha. It is an '81.

What are "WURs"?

Mysterytrain · 02-08-2007, 07:37 PM

on the right side of the engine there is a device called the Auxilary Air regulator. It is an automatic throttle of sorts. It allows air to bypass the throttle plate [an air leak] and cause the engine to run faster. It is controlled by a heating element inside the device and engine heat. If you do a search on AAR there is tons of info on troubleshooting.

toddu · 02-09-2007, 09:11 AM

I had similar issues on my '81. Turned out the AAR needed to be replaced, then the WUR had to be adjusted, then all the other pieces could finally be tweaked (mixture, etc). I was able to get a used one for $150.... they're not cheap new.

1982911SCTarga · 02-09-2007, 09:55 AM

Hank, WUR is an acronym for warm-up regulator, also referred to as a control pressure regulator (which, to me at least, is a more accurate description of what it does).

Do a search on CIS (continuous injection system) and you'll get lots of results.

A brief backgrounder on 911 CIS is here. If you're planning on being the crew chief for your new-to-you SC, I would suggest that you get the Bentley 911SC manual, which has a lot of good information about CIS baselining and troubleshooting. You'll also need to purchase or borrow a CIS gauge set (still available from different sources).

In any case, avoid the temptation to shotgun parts and fixes, which can result in a sore wallet and frustration. Work the problem thoughtfully.

Brian

Nostril Cheese · 02-09-2007, 10:04 AM

I had the same issue on my old SC. turned out to be the boot that connects the airbox to the throttle body on the top of the engine. It had some hairline cracks in it. Once replaced, it didnt hunt when cold. FWIW.

Mysterytrain · 02-09-2007, 10:27 AM

Any air leak will cause the engine to idle faster. You can easily test the AAR. You should have 12 volts on the electrical connector when the ignition switch is in the run position. Next, If you remove the outer hose [a bit of a pain if the A/C compressor is still on the car] you can use a mirror to look inside of the AAR opening. In its cold state, with no voltage applied to it, the opening should appear partially open. If you apply 12 volts to the connector by re-attaching the cable or with a 12 volt power source the opening should slowly close. The closing should take a couple of minutes. If the AAR tests good then you need to look elsewhere for the 'air leak'.

AAR Revisited
Now that I think of it..you could also have an issue with the distributor advance hanging up.

mede8er · mede8er's Garage

One word....carbs....

*ducks*

Mysterytrain · 02-09-2007, 12:15 PM

lol, yeah bet they make starting in 16 degree weather a joy

JP911 · JP911's Garage

Had a similar problem and it turned out to be the decel valve. It's easy enough to plug the decel valve to assess whether or not that is the problem. On your later SC the decel valve is a flying saucer-shaped thing on the right side of the engine. You can unplug the vacuum line from the valve and block off the valve and the vac line. If this doesn't help, then move on to the AAR. Then the WUR. Finally, when all of that fails follow the simple instructions provided by mede8r (I did!).

crashmy911 · 02-09-2007, 12:17 PM

yeah it might take longer then 20 minutes to warm up. Its reaally cold here. Did the car get totally warmed up or not?

mede8er · mede8er's Garage

All kidding aside I also have the 'cold start' syndrome....

Having just sold Ruby I am resurecting the Bluebird project and though I've got some PMO's coming I wanted the CIS well sorted so I could sell it....

After replacing most of the vacuum lines I pulled a test on it and guess what....no vacuum....zero, zip nada....not a squeak...

I am currently wearing out Bill Sims website for the vacuum diagram..

You may also find this handy....

http://members.rennlist.com/jimwms/CIS/CIShome.html

HDBrown · 02-09-2007, 06:27 PM

Thanks for all of the input. I'll study up and take a look at some of the likely culprits this weekend.

I drove the car three times tonight. The first time it warmed up for 10 min and I drove another 10-15. It never idled below 2200 rpm. The second time it was the same. The third time it was still warm and approx 30 seconds after starting it settled down to 900-1000 rpm idle... it never hunts, just doesn't seem to know when to idle down after warming up.

More later this weekend. H.