Porsche 964 C2

[Sunbumsurfer]

I was hoping someone could help with a 1991 Porsche 964 C2 Cabriolet. The car will run for quite some time fine but if I decelerate at some point (not every time) - the car starts to choke and sputter and cannot seem to get back in tune. Given time or shutting the car off and restarting 6-7 times the car will reset. My best guess is the Idle Speed Control Valve is not resetting and is not maintaining the vacuum. Has anyone run across a similar issue?

[nickd]

ISV only enters the equation when the throttle is completely shut (the idle microswitch is closed) and you are within the idle rpm range. All that it does is allow air to bypass the throttle, not exactly vacuum related. The idle microswitch, however, controls decel behavior. First check is to make sure that the microswitch is getting activated. It's on the throttle body. Easy to see.

Next thing to check would be swapping out the dme relay for a spare.

Pulling the ISV and cleaning can't hurt anything.

After that, I would start methodically checking all of the sensors. Unless anybody else has an idea?

[Nine9six]

I'm thinking dme relay as well...p1rolly a cracked solder joint causing intermittent fuel flow. Some shops even resolder the joints on new units, based upon the number of bad new units right outta the box.