SC doesn't idle high when cold

Well, I am back to square one troubleshooting my SC, which does not idle high during cold weather.

After rebuilding the AAR and getting it to the point that it worked when not bolted down but did not work when attached to the engine, Brian Haggard suggested that a small crack in the hose leading to the AAR could have been forced open when the AAR was bolted down. I just replced the hose, and he was right, there was a pretty bad crack. I'm disappointed, though, that the symptom is still there. THe car never stalls, but the idle fluctuates from about 10 rpms to 1000 rpms until the engine is totally warmed up.

Does anyone know of any other components that could cause this problem, other than the AAR or AAV? If it gets warm again before I fix it, I guess I'll have to wait until next winter.

Olivier
'82 SC

BRAINIAC Tyson told me about a rather strange problem he found recently on a CIS Porsche. The hose from the AAR that delivers auxilliary air to the air box was okay, but the fitting on the air box was not. Now, this fitting would be located AFTER the throttle body, near the cold start injector in the back on the dirvers' side of the air box. Anyway, this thing looked like a connection for a hose. Big one I think. But there was no air passage. The part had been casted as a plugged fitting (don't ask me why) and could not pass air.

------------------
'83 SC

Thanks, Superman, I'll have to check that out, too. I'm not ruling anything out at this point.

Olivier

Oliver, when Tyson told me the story I assumed that a PO changed the part using a used one off a differing model. It would be interesting to hear of two such incidents. You could detach the hose at the AAR and blow into it, I suppose, to see if air passes. Anyway, I wouldn't have even suggested it except that if the AAR is opening and the air is bypassing the throttle body, your idle should definitely increase.

------------------
'83 SC

My idle used to increase, though, so it probably isn't a totally plugged opening. I started the troubleshooting to fix the problem of an idle that stayed too high for too long (2000 rpm for almost 30 minutes of driving). It was probably the AAR that wasn't closing correctly, probably a loose connection and only the ambient engine temperature was closing it. After removing and reinstalling the AAR so many times, I'm sure I aggravated a small crack in the 18 year-old air hose to the throttle. Now that the hose is fixed, I guess I have to look for other vacuum leaks, or try the AAR or AAV route again. I'd rather have that problem back now rather than the low, lumpy idle on cold days, but it could be a lot worse. I don't dislike CIS, but it is really hard to troubleshoot! Do you know if any other components, like the WUR, cold start valve, etc. could be causing my symptoms?

Olivier

This may sound strange but check the vacuum hose to your vacuum retard. In fact, check the ignition timing period. If the timing is advanced too far at idle it affects the vacuum signal. That affects CIS to a great extent. The vacuum hose may have cracks, be unhooked, or the diaphragm in the retard on the distributor may be punctured.
I have seen this problem cause unstable and low fluctuating idles before.
Oh, and thanks Superman, for relaying my story!

------------------
Tyson Schmidt
72 911 Cabriolet

Thanks, Braniac, I will definitely check that. I can't believe how many vacuum lines there are in the CIS system!

I took the car on a 120 mile trip today, and it did not start out well. The engine was warming up finally, and I opened the trunk to stow some luggage. The engine immidiately began to run rough. Thinking it was just still cold and because we were already late, we headed off anyway. minutes later on the highway, I was wishing I had switched cars. The car was hugely underpowered and sounded completely wrong. As i imagined everything I could have screwed up while lowering the engine, from fouled plugs from cleaning the sensor plate and thereby adjusting the mixture inadvertently to broken valves, etc. Just when I was getting really discouraged at the near future of my engine, my wife noticed that the clock wasn't working. It was stuck on the time just before we left. Then it dawned on me that a fuse must have blown when I opened the trunk before leaving. Sure enough, no dome lights, clock, glove box lights, power antenna, or OXS SENSOR circuit!!! I was thrilled to realize that it was just a fuse. I pulled over and changed it and the engine immediately went back to a smooth running state with all power restored. Turned a miserable drive into a great one with the family, and we were still on time.

Anyway, just thought I'd share a strange fault. I would have probably lowered the engine again if my wife hadn't noticed the clock had stopped.

Olivier