Update! Re: Fuel system diagnostic help.

[M. Oesterwinter]

I just thought I would give a summary update on what has happened so
far.  The original message is quoted below:

I have replaced the spark plugs (with tri-electrodes), ignition cables,
rotor, and cap.  The wiring harness on the distributor looks to be in good
shape, and I don't hear anything obvious from the fuel pump.

After making the replacements I still had problems.  I then tested the O2
Sensor with a DMM, and got random readings from about 200 to about
700.  The readings seemed to oscilate up and down.  From what I
understand, this is good.  I was then told to test the 02 sensor under
load, so I tried driving, and I couldn't get it to exhibit the
problems.  Wow, I thought, mabey the problem is fixed.  Nope!

Tried driving today.  Still had DMM hooked up to the O2 sensor.  Once
again had problems.  02 sensor still gave fairly normal
readings.  Though the oscilations went higher and lower.

I disconnected the ground from the O2 sensor, and still have the same
problems.

I am thinking that this may be temperature related.  Last night when I
had no problems was probably the coldest point at which I tried it.  I
have had the most sever problems when it is hot outside or the engine has
been going a long time.

Also, the the check engine light DOES NOT come on....  What should I try
next????

On Fri, 22 Dec 2000, M. Oesterwinter wrote:

> 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
> 
>