930 cold weather idle problem

[JohnC]

With the coming of cold weather (morning anyway) my 930 ('77) is having problems idling. Initial starting in the morning is fine until the engine warms up and at that point the engine refuses to idle. Today the motor stalled, after being warmed up, while sitting at a stop light(I'm starting to get pretty good at heel and toeing).Once I got the car started it idled between 1600-1800rpms!

The only problem during the warmer weather would be an occasional high speed idle (3000rpms) during a warm restart.It would idle high then come down after about a minute. Otherwise it would idle
fine, a perfect 1000rpm, with maybe a fluctuation of about a 100rpm.

The warm weather problem is tolerable the cold weather is a real PITA.

Any ideas?
Does this sound like an AUX AIR VALVE or WUR?

[83930]

Had the same problem with my 930 when I bought it. After two months of looking up info on the cis system, and finally buying a test kit I found the wur to be the culprit. just had another problem with mine, the airflow switch was partially grounded and would not let the fuel pump come up to pressure, hence it would stumble and backfire when I would stomp the thottle from an idle.Only found it after the engine died and wouldn't start without disconecting the airflow plug.Just kind of interesting I thought. Put a test gage on the cis and you will probably find your problem.Good Luck.

[JohnC]

Thanks for the reply "83".

Over the holiday I started to "poke around" checking hoses for dry rot/loose clamps i.e. vacuum leaks. I had found that one of the hoses on the deceleration valve was not fully seated.It looks like the hose was cut just a little too short and could be allowing air into the intake manifold.I replaced the hose with the proper length and this seems to have fixed the stalling problem.

During my "poking around" process I also investigated the aux air valve.Since its easier to get to than the WUR. The resistance of the heater coil was zero which I checked against an Aux Air Valve I had inhand. Additionally once the engine was up to temp I unhooked the tube which runs from the intercooler to the AAV and looked to see that the valve was completely closed...it was.

The car runs very strong and idles nicely except that it often idles high(as I stated before 3000rpms)initially at warm startup, the idle returns to normal after a short distance.This does seem like a fuel pressure issue(WUR) but why sometimes and not others?

[wckrause]

I don't see how a WUR can cause a high idle (3000 rpm). If it's causing the mixture to be too rich, you'll get a hunting idle, if it's too lean you'll get a rough idle. Maybe your distributor mechancial advance or vacuum advance/retard is sticky.

[JohnC]

hmmmm...I did'nt think of that WC. That does seem to make sense. I have'nt removed the distributor cap since I purchased the car since I bought it(a year ago) and before that the car was sitting in a warehouse for some time. Next time I get a chance I'll check the mech advance.

I assume the 930 uses a typical mech advance mechanism (weights under the rotor moved by centrifical force).