[Fwd: New member needs help]

[J Norris]

Thanks for the reply.  The manual says nothing about a hitting limit on the TPS
voltage.  I did set a code 21 twice but only when the diacom was hooked up and
no other time.  The GM manual for code 21 says nothing of a high limit.  The O2
voltage at the time of the event was 4.98v.  The ECM was definitely in closed
loop.  The Int. was 180 and the BLM was 124.  I have never checked fuel pressure
while the supposedly lean condition was happening since it hit or miss.  Under
"normal" conditions the pressure was 45 psi at WOT.  Since I readjusted the TPS
max down to 4.63 volts max, everything seems to be normal.  What bothers me is
that I have talked to a half dozen so called Corvette experts and no one ever
heard of the TPS having too high of a voltage and kicking it out of PE mode.

    Rotten egg in the tank?  Never heard of that one before.  I balloon maybe
but not an egg.  Thanks again for the info.

David A. Cooley wrote:

> Jason,
> The popping was definitely from an extremely lean condition.  The High TPS
> could have been a problem, but without having a GM cal for that vehicle in
> front of my, this is only an educated guess based on what I have seen in
> other cals... The TPS has a high and low limit.  Exceed either limit and it
> goes back to closed loop because it thinks the TPS may have a problem.  I'm
> surprised the ECM didn't set a TPS voltage too high code.
>
> What did diacom say the TPS voltage was when it started popping?
>
> Also, a fuel pressure guage OUTSIDE THE CAR you can see while driving would
> help... Could have a bad conn. to the FP making it cut out and go lean as
> FP drops.  Also, some smart a$$ may have dumped a raw egg into your gas
> tank... when you accelerate hard, it slides around until it covers the FP
> pickup and cuts off fuel.
> Later,
> Dave
>
> At 02:22 PM 11/18/98 -0500, you wrote:
>
> >Hello everyone:
> >
> >    I am new to this list and I am looking for some help.  I have been
> >having a problem with my 89 Corvette L-98 6 speed.  For months now I
> >have been battling a problem that has been really frustrating.
> >Sometimes, when accelerating the car has no power at WOT and I have a
> >rapid popping/backfiring/missing thing going on.  I finally broke down
> >and got a Diacom and recorded the event.  When it happened at WOT, my O2
> >reading dropped to 0 and my integrator climbed to 180 while my inj.
> >pulse width was 9.5ms or so.  Now there was two thing I immediately
> >noticed.  One why the extremely lean condition and two, how come my Int.
> >and BLM were not 128?  I found the answer to number 2 last night.
> >
> >    My TPS voltage was .55 at idle and 4.98 at WOT.  The ECM will not go
> >into open loop PE mode at this high of a voltage.  At this high setting,
> >the ECM was trying to maintain a 14.7:1 air fuel ratio.  I readjusted
> >the TPS to 4.63 volts max and BINGO!  The ECM goes into open loop rich
> >condition.
> >
> >    Now, the million dollar question is could the high TPS voltage at
> >WOT cause the lean condition I am experiencing?  The fuel pressure is
> >fine (37 psi at idle 45 psi at WOT) but I never had an opportunity to
> >check it while the seemingly lean condition was occurring.  The fuel
> >filter is new, the injectors were leak tested and balance tested and the
> >O2 sensor is new.
> >
> >    I have Excel sheets I send if anyone would be nice enough to view my
> >data and try to help me.
> >
> >Thanks again,
> >
> >Jason Norris
>
> ===========================================================
>            David Cooley N5XMT           Internet: N5XMT at bellsouth.net
>      Packet: N5XMT at KQ4LO.#INT.NC.USA.NA   T.A.P.R. Member #7068
>        I am Pentium of Borg...division is futile...you will be approximated.
> ===========================================================