CIS throttle switch issues
 

Hey guys, So again here working on my 924 turbo CIS, and since theres a lot more activity here, hoping you all can provide some insight. has the same "TPS" as 911 SC with the 3 positions

I picked up a Smoke machine and there are no intake/vac leaks (found one but fixed it)

I have a dual adjustable WUR and have adjusted it every which way 1000 times. I think I almost have it dialed!

But what i could never get to go away was that I get a very rich condition on throttle "tip in" (which makes me have to slip the clutch to pull away from a stop) Finally for the heck of it I just pulled off the electrical connector to the TPS and that went away (now it doesn't run properly while driving, but at least give me some answers)

SO why does it do that??
If I have it tuned at 14+/- AFR, I understand it should go a little rich, but it goes to 10, immediately, its like the system just dumps fuel at tip in.


heres my TPS
http://forums.pelicanparts.com/uploa...1742275279.jpg

anyone have any info they can share?

anyone?

I got nothing for ya on the TPS testing but I’m just here to say thanks cuz I never knew there was a 924 TURBO

Try a PM to Tony (boyt911sc) if anyone knows about how to test the switch, he does.

The SC models 80 - 83 came both with a 2 position TPS.

1980 --> one at idle and one at acceleration (35°)
1981-83 --> one at 15°/mid load and one at acceleration (35°) (with this type an additional microswitch indicates the idling state)

ok well any idea on how to adjust whatever it making it go very rich "off idle"??

As this switch is part of the electronic motor management of your 924, you should let check the ECU first.

I guess i could see that if you dont consider the "idle switch" a position

If idle is set to closed throttle, I dont know how else to adjust??

Apparently this is also used in the 965.
Not sure how to play with the ECU here, this CIS is so antiquated. I see why people swap to carbs.

technically seen, "idle" is a position on the TPS.
You should not play with the ECU, you should let a service check it for you.
CIS is very reliable if all parts work well, no need to switch to carbs where her you will have other problems to take care of (i.E. consumption/mileage, synchronization, cold start etc) if using in a common street drive car

Was the ECU specific to US models of 924 Turbo? I've owned two of these cars. Both were 1979 RoW models and I entirely stripped one of them after it was totaled. I can't remember of any ECU in these cars. As far as I remember they used a very basic CIS system with no electronics except the CDI.

theres an early79/80 and late 931 81/82, the early one is "transistorized" and the later is "digital" (like a casio watch!)

I really need to get on the EFI conversion, just wanted to have it drive-able while I assembled all the pieces

heres what is in a "S2", second one is the "boost module" Like a KLR in the 944T
https://i.ebayimg.com/images/g/2YIAA...f/s-l1600.webp

https://i.ebayimg.com/images/g/CcIAA...D/s-l1600.webp

OK, I see now. Mine were very early models both dated from January '79 and were "only" putting out 170 HP, while yours is probably 177 HP thanks to this added electronics.

im thinking i may just short the "idle" switch and see what happens, hopefully at least it wont dump fuel in, ill let you know

Ok I connected the "idle switch" wire to ground and drove it and it no longer went full rich. just drove it down the st and back, need to tune it a little more, but at least thats something.