Fuel system diagnostic help.

[M. Oesterwinter]

I have an odd problem that I can not figure out.  It's '87 5000
Turbo Quattro.  Here is an explanation of how it came about:

About to go on a long road trim (250 miles each way), so I do an oil
change and do other little maintenance things.  After a bit of driving, I
touch the ignition cables, and the forward most one feels pretty hot.  I
figure its getting some extra resistance, so I go to my '85 turbo and pull
out one of the ignitional cables (just in case) and take it along.

Now I start on the road trip.  20 miles down, the car does a little
sputter/jerking once I get into the mid range RPMs.  So I stop and
switch out the plug cable.  It seems that the cables twist off at the
metal socket, so that is how I was able to get it in and out of the
loom.  I hit the road again and have not one problem averaging about 80-85
MPH the rest of the way there.

A couple of days later, we take a trip from there that is about 70 miles
away.  I am late, so I average about 90 MPH on the way there, but on the
way back, I was following people at 60 or so, and this is where I start
having real problems.

It started out that whenever I went over about 4K RPMs, it would sputter,
and I would loose power.  I pulled over, and found a hose that had
collapsed (not knowing when it had happened).  We tried as best we could
to get it open.  If I were to rev the engine, I could not tell if there
were any problems over the 4K RPM mark.  So we continued on, trying to
keep it under 4K.  But, this mark soon started to drift down.  I tried my
best to keep up with the cars that I was following, but I was having a
hard time.  About 20 miles later, I wasn't able to pass 2K RPMs.  So, we
pulled over and left the car there.  The next day, I got a ride to my car,
and it seemed to run fine as is most of the way back.  I stopped by a
parts store, and picked up a hose to replace the one that was bad.  I also
picked up a fuel filter.  Going back from the parts store, I think that
once again, I started to experience the sputtering problems.

Finally, got back and replaced the fuel filter and hose, and then drove
around, trying to get the temp up by driving harder than usual.  It seemed
to be fine, so I headed back.  Then later, I drove the car again, and once
again experienced the problems.

I am being an optimist now, and thinking, "Oh, it's probably just a few
air bubbles that hadn't escaped the fuel filter yet."  So when it comes
time to head home, I think that I will do fine.  Odly enough, I made it
the first two hours just fine.  Then the problems started again.  Once
again a little sputtering/jerking at about 4000 RPMs (or mabey a little
more) started.  That mark slowly went down over the coarse of about 40
minutes, until I had to pull over.  I pulled over, and the car died.

I tried to start it again, and had problems.  When I was able to start it,
I had to keep it reved or it would die.  So I turned it off, and sat there
for about ten or twenty minutes.  Then tried again.  I couldn't tell
anything by reving it, so I started to go.  It seemed to do okay for a
short while.  (Once again having the 4K RPM cap.)  A little while longer,
and I had to pull over again.

I looked at the ignition cable that I had replaced.  I actually unscrewed
it from the metal socket.  It seems that it didn't have a very good
contact because the insulation material was melting.  I cut the end of the
cable off to expose some bare wire, and I tried as best as I could to
screw it back in there.  At this point, the car did fairly well again for
a while longer (I don't recall if I had the 4K cap, but I don't think
so.)  Then it started to have problems again.  I pulled over and looked at
the cable.  It was once again melted.  I cut it off again, and from here
was able to drive all the way home.

Now, I am not very good with cars.  I have no clue why it would have had
such extreme problems if just one cylinder was not firing.  I think I even
disconnected the plug altogether and didn't have the problems that I was
having, so I am very confused why replacing and cutting the wire had
helped so much.  Not only that, but I replaced the entire wire set in the
mean time, and I am still having problems.  After about 10 minutes of
driving, it starts to sputter and jerk.

Now, the only thing that comes to mind as potentially being the problem is
the fuel pump.  What do you guys think?  Any advise would be very much
appreciated.

Thanks.

- Marcus