[Fwd: New member needs help]

[David A. Cooley]

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

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           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.
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