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-   Porsche 964 & 993 Technical Forum (http://forums.pelicanparts.com/porsche-964-993-technical-forum/)
-   -   another idle/ISV question (http://forums.pelicanparts.com/porsche-964-993-technical-forum/1007374-another-idle-isv-question.html)

G50911 09-09-2018 02:11 PM

another idle/ISV question
 
so i have a newly transplanted 3.6 in my 71. it was running and checked out ok when i bought the motor 2 years ago so i wasn't expecting this much trouble from it. what i read about 964 motors (ISV, DME, etc) even perfectly running motors can be finicky so trouble shooting i go...

here's what's happening:
1) car fires up after a few cranks (shouldn't it fire right up on first crank?)
2) runs for a couple seconds then quits

i cleaned out the ISV and noticed there is a sleeve or something inside that doesn't seem to slide. is it supposed to or is this stuck?

there's also what looks like a vacuum port not connected to anything and i feel a lot of air being pushed thru when it stalls.

any ideas?

http://forums.pelicanparts.com/uploa...1536531057.jpg

Paperboy 09-10-2018 04:50 AM

Is the ISV off the car? You can test it by connecting a small low amp 12 v battery ( camera type)to it quickly . You should hear a click as the valve rotates. You can clean it carefully w carbcleaner. It is adviced not to lubricte it.

G50911 09-10-2018 08:18 PM

yeah it’s off the car and i tested it. seems tomwork fine. i noticed that after 5-7 seconds of running it just dies. almost like the fuel pump loses power or maybe the dme cuts out. any thoughts on what it could be?

Paperboy 09-13-2018 10:14 AM

The vacuum port is part of the oil tank ventilation. If I remember the 964 has two vacuum leads from the oil tank, one thicker that connects to the intake after the air flow meter but before the throttle body, a second thinner one that connects right after the throttle body which I think is the one your are missing. My guess is if everthing else is ok the car should idle ok if you just try plugging it. If not the other lead might be missing / not connected as well.You would need to check the oil tank vent setup on your 71 so all is ok for driving with the 964 engine. I guess ideally compare diagrams for both cars.


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