[s-cars] Misfiring?

[The Gagnons]

Hello,

Last Friday I had a problem with my 92 S4.  The car would seem to misfire
under acceleration and run fine at idle and light throttle.  It started
after about 10 miles into my trip and seemed to get progressively worse.  I
could drive the car if I babied it and did not give it more than about a 1/2
inch off idle.  I got to my destination (15 miles total), picked up my stuff
and proceeded to drive back to town .  The car ran fine for about  2-3 miles
and then started misfiring again.  I again babied the throttle and parked
the car at a local restaurant where I met my family for dinner and a movie.
After the movie I drove back home and the car misfired again under
acceleration after about 7 miles.  I swapped the POS modules with my wife's
S4 and then drove the car again Saturday morning and it did not misfire
until 8 miles into the trip.  I concluded that the POS modules were not the
problem.

The car was pretty low on gas during this whole episode, so I filled the
tank.  The low fuel light came on just as I pulled into the station.  The
car took 18 gallons.  The misfire has not happened again since I filled the
tank.  I just had the fuel pump replaced the week prior and it was the first
time I had run the tank low since the repair.  The new fuel pump was pretty
noisy after the replacement so I stopped by the shop to ask the mechanic if
he thought the misfiring was related to the noisy fuel pump and if he had
any ideas about what was causing the problem.  He said it was not likely to
be the fuel pump and some pumps are noisier than others.  I told him I could
hear it 3 feet away from the car and agreed that it was a noisy one and
offered to warrantee it if it was too loud.  He said the misfire was
probably a bad coil.

I have now driven over 70 miles without a misfire and am wondering if the
fuel pump was not seated properly and the pick-up was sucking air as the
fuel sloshed around in the tank.  I did inspect the coils and one had a
pretty bad gray spot that indicates leakage.

Anybody know if it is possible to install the fuel pump too high and create
the problems I described?

I intend to run the tank low again to see if the problem reoccurs.  If it
does not reoccur, I will replace the coil.
  I just hope I don't get stranded in the meantime!

Any and all advice appreciated!

Jack

---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.522 / Virus Database: 320 - Release Date: 9/29/03