skruggs964

I noticed that my '91 964 seemed to be running a little rough and wanting to stall out at stop lights, so I changed out the DME relay and replaced the fuel filter. When I took off the fuel filter, the gas that came out of it was black as molasses.

Is this a normal sight when replacing the fuel filter?

Thanks!

Geoffrey

Black colored fuel is not normal unless someone put in some black dye. I'd invistigate further and you may want to cut open the filter and check it out.

Gary R.

That's what came out of my track car's filter when I was trying to diagnose a "cutting out" problem at Summit Point a couple weeks ago (ran 4 laps, then would start sputtering, repeat same for every run group). We cut the filter open an found nothing, but upon removal of the tank sump screen there was some black gunk (kind of like dissolved undercoating) in there. We flushed it out, put on a new filter, and it did exactly the same thing 1st run the next day... being diagnosed by Dan J. now, sure hop it's ok at the Glen June 7th!

You may want to check the idle microswitch, my 964 did the same thing, I sprayed mine with contact cleaner and messed around with it a bit, all was well. It also wasn't starting as well at the time (had to use the throttle vs. the usual no touch/instant start/raised idle)..

Richard Curtis

GaryR: can you describe the idle microswitch and its location? Would it be noted on the PET?

Gary R.

Richard -
The Idle Speed Microswitch (called the closed throttle switch also) is mounted on the throttle housing just to the left and below the Idle Speed Control valve. If you move the throttle forward by hand you will see a flat portion of the linkage (on the right side) that actuates the switch. You can stick you finger in there and feel the switch click when you press and release it. The wire that feeds it goes to a plug just to the right/below and in front of the Idle valve, can't hurt to clean that also. You also should look at the Full Load Microswitch (WOT Switch) as if thats stuck it keeps the car in Open Loop mode (ignores the oxygen sensor) and can cause a myriad of issues also. It's located on the opposite side of the throttle body, just follow the "Y" plug wire that goes to the Idle switch, the other one goes to WOT switch..

All of this information is in Adrian Streather's "Porsche 911 Enthusiats's Companion", all 964 owners should have a copy!
ISBN #0-8376-0293-9

JasonAndreas

skruggs964

Thanks guys....much appreciated! I'll keep you posted on what I find.....

Richard Curtis

GaryR: I have Streather's book, in fact, have read it thoroughly several times. But missed that (or else forgot about it) and didn't think to check it again. Thanks much and I really appreciated the photos.

Gary R.

Yep, Jason came through with some great pics!