I just had another idea. In the 80's the T44 series had a problem with the
inside of the fuel tank (lining) flaking off and clogging the intake screen of
the fuel pump. The problem had the same symptom as you describe. Later in the
series the tank was changed to a molded plastic with no liner which cured the
problem.

If your 90 has one of the tanks made like the T44's tanks this would be my best
guess as the source of the problem.

The factory recommended fix for the problem was to pull the fuel pump and cut
off the intake screen. The result is that the particles are pumped through to
the fuel filter. After that you should change the filter several times in the
next six months or so.

Tony wrote:

> Intermittent fault in the hall effect module (distributor)?
>
> Maybe a current load heats up the fuel pump relay causing it to fail
> then recover when it cools.
>
> Differential fuel pressure switch on the front of the fuel distributor
> can be intermittent.
>
> Vacuum leaks?
>
> Clogged fuel filter?
>
> wrote:
>
>> My 89 Audi 90 quattro has this strange problem. It starts right up and
>> runs strong for about 25-30 min. Then it stalls out. Start it right
>> back up and it will do it again. No matter how much you press the
>> accelerator it will make its way to stall in a few seconds. the fuel
>> pump does tane to make a louder buzz as it warms up. I feel that the
>> pump is not the problem becasue I drove a CIS Jetta for 3 years that
>> did the same thing. Any ideas.
>>