Gets rich for 30 sec's after statup when cold

[T86951]

My na '86 944 starts great and no flooding on start up, hits and starts right up fine.
Then in a couple seconds it gets really rich and chugs and puffs black smoke for about
20-30 seconds and clears up and runs fine. I thought a leaking injector but pulled my
plugs after startup and they were all 4 totally black. Pulled the fuse and ran it out of fuel preasure and let it sit overnite and it did the same. The colder it is the worse it is. I have checked and an '86 doesn't have a cold start injector. Help, has anyone else had this problem?

[lm6y]

The only thing that even comes close in the Bosch Fuel Injection & Engine Management book is the thermotime switch. E mail me, and I'll try to send you a scanned copy of the test procedure.

[T86951]

Thanks for the help, my Haynes manual says an '86 944 has a engine temp sensor, idle control valve, throttle position sensor, air flow meter sensor and Oxygen sensor. It doesn't say anything about a themotime switch. I read that those are used on the older CIS injection systems up thru '83 on 911s and 912's and thru '82 on 924's and 928's. Does that manual cover Motronic injection systems?
Thay was really great of you to look that up in your manual but my car doesn't have that switch. if you see anything like my symptom for a Motronic system please let me know. Thank you very much again, this is driven me crazy. Wonder what that switch would be in the Motronic system?
Thanks again

[T86951]

Shouldn't an '86 944's rpm's increase on cold starup and stay increased for a little while? Doesn't the idle control valve let more air in the intake? That what the haynes manual says anyway. What does everyone elses 944's rpm do on a cold startup as far as rpm's? I am thinking my idle control valve (small canister under the intake) may be bad leading to the rich condition for about 30 sec's on startup. Has anyone else had one go bad and what did it do?

Thanks
Dan

Thanks

[porscheboi928s/c944t/n]

did u adjust the knob on the comp.?? mine does the same thing though i can't play with it now(winter). i will be checking it come springtime...by the way it is my daily driver

[T86951]

I don't know what knob youa are refering to?

[T86951]

can anyone help me? I am now thinking my computer may be bad as I read something today that said if it gets really rich it has to be your DME. I am at ropes end on this. Hasn't anyone had this before?

[porscheboi928s/c944t/n]

been having the same problem...but what car does is when i pull up or let say idle..it will run rich..but since i played/tweaked the knob on the side of the dme box 3 position.. i turned it back to 1 position and never seen it running rich again....but i like the way it feels on the 3 position so i put it back again.... my 2 cents..hope this helps ...

[T86951]

Thanks, It may be you idle control valve, I don't know, Mine is just seconds after start up and then for 30 secs and then it idles and runs fine. These are hard problems to sort out.
Good luck