Quick CIS Fuel setting question
 

I know I should do a search. I hate this search engine...:D

I have a hunting idle at cold start. When I pull gently down on the throttle plate it goes away and idles at 1250.

This means that I am slightly rich?
Turn mixture screw CCW?
By how much would I start? 1/16, 1/8, 1/4 turn?

Thanks for a reply from the collective consciousness.

Michel

DON'T MESS WITH THE MIXTURE SCREW!

Yes, it sounds like a rich idle but during cold starts, that's usually a problem with the warm up regulator. Your first order of business is to check your fuel pressures with the appropriate gauge set and compare your cold control pressure with the chart for your particular wur and ambient temperature. Without adding anything more to possibly confuse you, let us know if you have any questions about checking fuel pressures and if not, report the pressures you record.

No worries. My WUR is perfectly alright. Just your bi-annual tune up re changing atmospheric conditions...but as I am unable to keep left from right I always forget if CCW is lean or reach and if pulling down or pushing up is causing hunt/stall/improvement.
i should write it down somewhere.

This is a non 02 SC with vac assist to the WUR.

ccw lean

I'm certainly no expert on CIS but from my limited experience, having to adjust the mixture screw bi-annually usually means there are other issues that have not been addressed. Porsche provided a plug for that screw for a purpose. That is not to say your mixture doesn't need adjusting, but once it's set, and if the rest of the system is in spec, it should not have to be touched for "changing atmospheric conditions" (unless, perhaps, you are moving to/from altitude.)

You certainly know your car better than I, and I don't question your knowledge of it's workings. I am only offering my insight from my own experiences and the suspicion that continually adjusting the mixture screw is covering up another problem.

Perhaps ,but I revised the entire intake system with all new gaskets on just about everything and the car behaved in exactly the same way. I must have tested all the components at least 3 times on opening times etc...
I just seems to need a little adjustment when it gets very humid and cold and when summer is here.

I am putting it down to a non O2 car and old age both of driver and car.

Michel

The stock mixture setting is purposely on the lean side to comply with passing smog. The sweet spot for mine is more on the rich side. I also adjust the mixture seasonally as it is kept about 1/12 of a turn from rich oscillation when cold. This phenomenon is enhanced with minimized CIS components. My engine has had every component removed that is not essential for operation.
Yes CW = rich and CCW = lean
It is best to start and stop the adjustments going CW as it relieves possible bind in the mechanism, then blip the throttle and note the response.

thats how i have set mine, right on the edge of surging. also make sure the RPMS dont dip down then come back up when you let of the gas.

I have indeed the impression that it is only a small turn between hunting rich and spot on. Wish they could of made it a bit more articulated.