CIS Theory Questions

[sjepps]

1981 SC Targa CIS with Lambda sensor (Fresh re-build plus 300 miles):

1) For cold idle after initial start to function; metered air must bypass the throttle plate via hose connected at the top boot, through open AAR, through metal hose into the throttle body where the cold-start injector is connected. Correct?

2) If #1 is correct, then the cold-start flange must provide an open air passage into the intake below the throttle plate. Correct?

3) If #1 and #2 are correct, then shouldn't the passage thru the flange with the air flow shown below have an opening?


Thanks for any reponse

[clevy70911T]

I had pondered this same thing. I suppose the CSV would pass both fuel and air through same opening on the valve. It seems it would have to. ?????

[sjepps]

The reason I posted the above question is that I've been investigating a cold/warm up idle problem (no increase in idle after cold start) and removed all the air bypass components. (AAR, AAV, decel valve and associated hoses to verify each component's function) All have checked out as functioning properly. Also cold and warm fuel contol pressure readings are also correct. (54 psi warm, 25 psi@50F & 74 psi supply) and the car runs fine after warming up. When I removered the cold-start flange and valve I noticed there is no way for air to enter the throttle body because the flange hose connection has no openning. Either this is normal and I don't understand the air bypass system or the flange was manufactured incorrectly. I need someone to verify whether the flange should have an opening or not.

Thanks; sjepps

[tsuter]

Originally posted by sjepps
When I removered the cold-start flange and valve I noticed there is no way for air to enter the throttle body because the flange hose connection has no openning. Either this is normal and I don't understand the air bypass system or the flange was manufactured incorrectly. I need someone to verify whether the flange should have an opening or not.

Thanks; sjepps

Better get a new one.... or look again. The hose connection nipple and air hole thru the CSV flange is about 1/2" in diameter.

[Hladun]

Very useful site;

http://members.rennlist.com/jimwms/CIS/CIShome.html

On cold start valve page, there are two flanges shown. One with a hole for air and one not. Someone may have "fixed" your car with the wrong part!

[sjepps]

Tsuter, Hladen:
You are both correct. Appearently somewhere in the last eighteen years I've had the car the wrong part got installed. The part I have has no air hole like the early one shown in Jim William's site. Ordered a new one from our host. Maybe that will solve the cold start idle problem I've been chasing for two weeks.

Thanks for the help.

[RarlyL8]

Jim lives right here in Huntsville. Give him a call, he loves to talk Porsche tech. The HOD PCA is having a Tech Session at Jim's house March 5th. You should attend. I'll be there.

[Paulporsche]

sjepps,

Sounds like your AAR may be out of spec. Check a recent thread by mysterytrain in which he fixed his.