964 stall
 

First time poster long time reader. I've got a 90 C-2 78000 miles. I recently had a batch of stalling problems, which led me to replace the DME relay, Head temp. sensor, air flow meter plug drilled and adjusted, and the OX2 sensor replaced. Car ran very sweet for 1500 miles. Heres the new development. When fuel gets below 1/4 tank full, engine stalls on compression third gear down hill. no throttle response at stop and idling. I fill the tank and the problem dissappears until I reach below 1/4 tank fuel, this has happened three times.
Fuel pressure was reported to be a little high by my mechanic the last time in but told not to worry about it.
I am stumped. Any suggestions? Ben

Sounds like fuel contamination. Replace the fuel filter, and cut open the old one. If you see water or goo, the gas tank needs to be cleaned. It rains a lot in Portland, so it is not a big surprise to get water problems.

I wholeheartedly second springer's evaluation. Probably just an accumulation of gunk in your fuel tank moving forward to restrict fuel flow when you're on a downhill slope.
Brian

Maybe something funny with the tank ventilation system, e.g. clogged vent causes low pressure/vacuum in the tank as the fuel level drops? You could try temporarily running at 1/4 tank with the fuel filler cap removed and see if that makes a difference or provides further clues.

Partially clogged fuel pickup in the tank? (full tank provides higher fluid pressure at the pickup, like what your ears feel when you dive to the bottom of a swimming pool).

Good luck, let us know what you find.

Thank you gentlemen!! I will look into all the above. and post a follow up Ben

I knew someone who had trouble with his 911, where in certain turns on the track the engine would start sputtering from being fuel starved. Turned out, over the years, there was an accumulation of gunk in the gas tank that would roll around and cover up the fuel outlet from the tank. Where it came from, who knows, but cleaning the tank out took care of the problem.