Maybe you could swap out the injection system and install CIS?
J/K

I am very wary of fuel system cleaners. Usually they do more harm that good as some tend to wash stuff off the inside of the tank and put it in the fuel filter.
This is even more of a problem on older cars, especially ones that have sat for a long time.

+1 on water in the fuel. Fuel system cleaner may not remove moisture. I don't know if they sell the methanol style in CA, but around here in winter it is the only thing that will remove the water. FF is a must change.

"GIAC rewrote the assembly code (not a map adjustment) to turn on the O2 sensor monitoring circuitry."

????? So they claim, as with many of their other claims that prove hyperbole,
but not in actuality as determined by extensive 959 DME testing.

"Finally, GIAC incorporated a software timer into the programming (in the chip) to delay premature activation of the O2 sensors."

Right, which basically indicates that it's really nonfunctional!

And if Giac really had a solution, then why did Canepa do a Mickey Mouse
and ruin the collectivity by using Motec as a solution?

Bottom line: A brute-force mod, i.e. they just super leaned the mixture.

I say water in your fuel also.
Troy

Since the problem started just after the fill-up, my first instinct is bad fuel. As the others have said, I'd start with draining the gas and replacing the fuel filter.

My $.02.

you may be able to give a quick call to Mr. Canepa and talk to his 959 system guy... maybe they have a few ideas or things they have run into. my 1 cent

Hmmmm
1 Car runs fine
2 Car filled with suspect gas
3 Car runs like crap immediately afterward

It could be a coincidence that the some of the vacuum lines and some of the fuel delivery and ignition ancilliary devices decided to belly up within 2-3 miles of the suspect gas station...

Can you find out why the gas station became "closed for maintenance"? Perhaps they got busted by whatever CA enforcement agencies for maybe playing around with the fuel composition.

Wayne,
I ask a buddy of mine Danny ( He owns P3 Automotive ) and he said this to me in a e-mail.. I hope this will help you out some.. he s a very knowlegable guy..

Quote Danny
Danny said:
"The first thing I'd look for would be vacuum leaks. that car has a LOT of plumbing that could easily be leaking at it's age. He should buy a diagnostic smoke machine. The machines are are about a grand. it's possibly the most valuable tool I own. I wouldn't spent I second speculating or guessing about vacuum leaks, I'd simply hook up the smoke machine and see. Mine finds the most miniscule of leaks in about 30 seconds. I often find leaks that are so small they aren't really casuing problems. i'd bet money that he'll at least find some small ones. I'd be happy to help figure it out if he still needs help".


Danny L King
P3 Automotive
445 Miamisburg-Centerville Rd
Centerville, OH 45459
http://www.p3automotive.com
turbotech@p3automotive.com

I filled my car with 91 at the same Chevron, within a day of Wayne, and my car runs fine. My prediction is that the problem isn't the fuel.

Not methanol
 

Use only isopropyl dry gas. Only iso will actually mix with the water and burn through the engine. Meahanol will not.

My spidey sense is tending to lead me toward plugged catalytic converters now too.

You mentioned that there are cats installed inside the mufflers. Hass all of the fuel that this thing been run on been unleaded?

The same 4runner that had the fuel filter problems also suffered a plugged up cat and it too would idle but had a terrible miss and lacked power. This truck had a similar number of miles on it as your 959 when if gave me all this greif (I got it as a roll over with under 6000 kms on it and it was 5 or 6 years before I got it on the road).

Uncle,
How would that be consistent with the high top end power? Plugged cats would kill power and boost. Usually plugged cats get worse under heavy load.

I'm guessing TPS or idle switch. Vacuum leak seems like a strong possibility, alternatively.

Doug

Milk just sprayed out my pop-off valve.

More info - not a gas problem, some type of electrical problem, new thread started here:

http://forums.pelicanparts.com/porsche-911-technical-forum/379626-still-stumped-959-fuel-injection-problem.html#post3611560

-Wayne

DWSD - my thoughts are that a 959 is pretty damn powerful, you might not notice if the power was down by 30% or so unless it was your daily driver or you had it on a dyno.

At the track I was slowly creeping up on another car that had 400 HP, so I'm guessing the power is on track at the upper rpm ranges...

-Wayne