Engine surge when cold

[dugsud]

Think I've read something about this in the past but I can't seem to find it.

83SC runs perfect when warm but idle speed surges from almost stall to 7-800rpm for the first 30 to 45 seconds when cold.

Any ideas? [&:]

 

[bones]

Timely you should mention this Doug as I feel I may have 'cured' this part of my 911s warm up process, see my 911SC Running Report of yesterday. As far as I know this is a common occurrence for many Carrera 3.0s , SCs and even 3.2s. Mine has always done it and it has become worse over the years till recently. As you may know I have replaced all gaskets and hoses on the top of the engine and in the CIS system as well as thoroughly cleaning the injectors and manifolds. The result is the engine doesn't 'hunt' on start up, it just fires first twist of the key and idles at about 1200 rpm. I'm interested to see if cold weather makes any difference.
I think curing the vacuum leaks and a thorough cleaning of the CIS has made a big difference to the smoothness and general running of the engine. What's the state of your engine?

 

[dugsud]

Hi Bones
My engine runs superb in all situations, It's just had a full service & as it runs so well I'm a bit reluctant to mess with it too much in fear of upsetting something else.

Cold surge is just a bit annoying though. If you were to name the most likely first thing to check what would you say?

I'm setting off on a two-week tour of France/Germany next weekend so I probably won't try anything till I get back.

Doug

 

[bones]

To be honest with you I don't think there is that much you can do with the engine in. I would say replace all visible vacuum hoses and the fuel injector o-rings. If you can check the tightness of the intake manifold nuts and check the condition of the six manifold/throttle body boots.