[Fwd: New member needs help]

[Bruce Plecan]

-----Original Message-----
From: Walter Sherwin <wsherwin at idirect.com>
To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
Date: Wednesday, November 18, 1998 8:18 PM
Subject: Re: [Fwd: New member needs help]

Is this the procedure for the small cap HEI TSB?
Bruce


>Jason...........You might want to examine your distributor very >closely.
The early 90's distributors of that style were prone to a >number of
maladies which tended to create the exact symptoms >you have described,
since their "Reference Signal" is the >heartbeat of the entire fuel
injection system.
>
>In this order..............1) run the car with the EST timing connector
>disconnected and note whether or not an improvement exists.    2)  examine
>the timing mark, with a timing light,  both with and without EST connected.
>Is the timing stable?   3)  with the EST disconnected, and while watching
>the timing mark with a timing light, look for an ever so slight timing
>advance with increasing RPM.  Then look for a gross timing shift of +6
>degrees at 2000 RPM or less.  If the timing initially retards,  or
>experiences the gross shift at more than 2000 RPM, then your distributor is
>bad.   4)  if all of these checks are okay, then your distributor is okay,
>and your problem is elsewhere.
>
>Stay in touch..............
>
>
>
>-----Original Message-----
>From: David A. Cooley <n5xmt at bellsouth.net>
>To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
>Date: Wednesday, November 18, 1998 3:12 PM
>Subject: Re: [Fwd: New member needs help]
>
>
>>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.
>>===========================================================
>