1976 911S CIS issue/question

[billh1963]

Encountered a new problem with the 911 (2.7 original CIS). Engine rebuilt 3000+ miles ago. I believe this is CIS related.

The engine has always surged at idle when cold...sometimes to the point of shutting off. To mitigate that, I would typically use the accelerator to keep the revs at 1500 to 2000 for a minute or so and then all would be fine. Cold in my area is typically 50F and above ambient temps.

Last weekend I took the car on a 50 mile drive. When I was a mile from home I pulled up to the stop light and the engine died. Hmmmm...never had that before. It started fine (with application of a little throttle) and ran good until I came to a stop sign. Engine died gain. In fact, it did it several more times until I got home. At speed engine seemed to be okay. However, would not idle for more than a minute or so without dying.

Had some time today so went to the garage to see what was up. Car started as usual and after idling fine for 20 seconds or so started the surging (as usual). Restarted and warmed up the engine as before. Started to take the car for a drive and before I could get to the first stop light the car died at idle. Being a coward I returned home.

So, symptoms are:
1. Surging idle when cold (has been this way since I've had the car both before and after engine rebuild..would like to fix)
2. Engine dies at idle when warm. Idles at normal rpm and then dies or dies when pushing in the clutch at a higher rpm and engine dies on the way down to idle speed.
3. At speed the engine is fine. No apparent fuel issue
4. Nothing changed up to this point. Last change was changing points a couple hundred miles before this issue started occurring. I did check dwell and it's spot on.

I read through the component failure description of the 911CIS primer and don't see anything matching this symptom.

Thoughts?

[rwest]

Check your points and ignition system as well. I had a bad tiny wire off of my points that had an internal break and it would run at higher rpms, but die at idle.

[pmax]

Check the fuel pressures.

CIS Troubleshooting for Dummies

Air leak next.

CIS Troubleshooting for Dummies

Report your findings.

[T77911S]

you are running too rich for some reason. I would suspect your WUR is bad.
check pressures as said.
you also have a thermo time valve (TTV) located near the WUR. check to see if you can blow through after the engine has been running for a minute or 2.
OR, remove the vac line from the TTV to the WUR and check for vac at idle

where are u in SC

[billh1963]

Orangeburg area....