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Join Date: Nov 2013
Location: sf bay area
Posts: 846
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?

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1967 911 (Burgundy Red) - #308439
1971 911 (PTS Black) - Built 3.6 Sleeper
1989 911 (Grand Prix White) - Cabriolet Bone Stock
Old 09-09-2018, 03:11 PM
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Location: Torquay , UK
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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.
Old 09-10-2018, 05:50 AM
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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?
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1967 911 (Burgundy Red) - #308439
1971 911 (PTS Black) - Built 3.6 Sleeper
1989 911 (Grand Prix White) - Cabriolet Bone Stock
Old 09-10-2018, 09:18 PM
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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.
Old 09-13-2018, 11:14 AM
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