SE Cold Start Surging

[Rpostma]

I have a 1982 SC and when I cold start it the idle surges only for the first couple minuets. Buy the time I back out of the driveway and go 500 yards the surging stops and does not reappear on subsequent restarts. Not a big problem but would be nice if it didn't do it. Any ideas?

RON

[psalt]

RON,

The best advice is to avoid guessing and do the test routine on the CIS lambda system to see if the system is working properly. This takes about ten minutes with an analog dwell meter. Most cold running problems on 82 911SC's are a combination of too lean mixture and not enough ignition timing and can be adjusted out by someone with experience with the system.

[T77911S]

fuel pressures need to be checked

[Joe Bob]

CIS is a fuel pressure sensitive system. Vacuum leaks are a bugaboo as well. Leaks have been known to lessen when an engine gets warm.....

[tcar]

Classic symptom of running too rich on a CIS car.

Lean it out slightly; see if it goes away; I mentioned it to my Pcar mechanic and he leaned it out slightly. Voila'.

[T77911S]

never adjust the mixture without first checking fuel pressures and checking for air leaks, there is a reason the mixture has changed.

[Rpostma]

Any clues on were to look for air leaks? This was present when I purchased this car in February this year.

[stlrj]

Air leaks are the same as vacuum leaks and they cause leaness which is not the problem.

Too rich will cause cold surge which is easily cured with a slight adjustment of the CO mixture screw.

Next question: do you have the 3mm allen to make the adjustment?



Cheers,

Joe

[Rpostma]

I am sure I have a 3mm allen but does it have to be anything special?

[stlrj]

Originally Posted by Rpostma

I am sure I have a 3mm allen but does it have to be anything special?

Just long enough to get into the invisible CO hole. The "T" handle allen tool is the usual one that our host sells.

[Rpostma]

Which direction do I turn it to lean it?

[boyt911sc]

Originally Posted by Rpostma

Any clues on were to look for air leaks? This was present when I purchased this car in February this year.

Any where air could get in is a possible point of interest. Air box, vacuum hoses, pop-off valve, injector seals, etc. See picture below:


Could you imagine how much unmetered air is going through these orifices? So adjusting air mixture to compensate for 'lean condition' is not the correct approach. Fix the leak/s and measure the exhaust with a gas analyzer.

Tony

[T77911S]

if the control pressures are wrong, the PO could have adjusted (richened) the mixture to make it run better warm, making it surge when cold. this is why you NEVER adjust the mixture until you have at least checked the control pressures.

tony has showed you air leaks around injector Orings and sleeves. you can save time and headache and just replace those, along with the intake manifold gaskets, rubber intake runners, O ring under throttle body, vacuum lines. and be sure to check any metal vacuum lines behind the system that go to the aux air regulator (in the pic).
did i miss anything?
dont forget about the vacuum line to the brake booster. i checked mine by pulling a vacuum on it with a hand pump and letting it sit.

[stlrj]

Originally Posted by Rpostma

Which direction do I turn it to lean it?

CW=rich CCW=lean