[Diy_efi] EPROM damage?

David Daniel ss396 at pinn.net
Sun Apr 11 02:35:23 GMT 2004


Brendan,
  I'll double check all of my power leads and grounds again.  If I'm reading
my ECM wiring diagram correctly, all of the sensors ground into the ECM
itself, and then the ECM has a ground?  I'll check each one individually
just to make sure.

  I do have a service engine light hooked up.  I wired it into the factory
light in the dash.  What really has me baffled is the fact that, with the
factory ECM and the replacement ECM, the SES light stays on the entire time
the engine is running, but only flashes a code 12 when I jump the ALDL
connector, and I get no response from the TPS.  When I use the Caprice ECM,
which is for a TBI 350, the SES light acts normal.  It comes on with KOEO,
goes out as soon as the engine starts.  I also get the "pump shot" when I
move the TPS lever while using the Caprice ECM.  The common thread between
the original Monte Carlo ECM and the re-man replacement is the EPROM chip
and the CALPAK(?) chip.  Also, once the engine gets up to operating temp,
while running the Monte ECM, the idle speed surges like the ECM is hunting
for a good idle speed.  I don't have a tach hooked up, but I'd guess that
the idle fluctuates from about 300 - 1000 RPM's.  I found and repaired one
vacuum leak this afternoon, but it made no difference in the way the engine
ran. I really think my problems started when I got impatient with the
battery.  It was dead when I wanted to check my power connections, so I
connected a battery charger and started putzing with the wiring.  That's why
I think I fried the EPROM, if that's possible.  This engine ran perfectly
while it was in the Monte Carlo.

Thanks,
Dave


Check your powers and grounds to the ecm.  Check the 5v reference and
grounds at your map sensor, tps, etc, make sure they are all getting
grounded.  U said you got no codes out of it.  Do u have a service
engine light hooked up? If so..make sure it is working...should come on
when the key is on, but engine not running, and go out a few seconds
after starting.

I just recently put a 4.3 tbi in a 81 chevy pickup, had it running in
just a few hours after dropping it under the hood.

If you need a schematic of the pcm, let me know, I work at  a Chevrolet
dealership and can get all that stuff should you need it.


Later,


Brendan Patten


Message: 1
Date: Fri, 9 Apr 2004 23:25:58 -0400
From: "David Daniel" <ss396 at pinn.net>
Subject: [Diy_efi] EPROM damage?
To: <diy_efi at diy-efi.org>
Message-ID: <GPEPJIFKINGINCMGPDEJMEAOCAAA.ss396 at pinn.net>
Content-Type: text/plain;	charset="iso-8859-1"

Hello,
I'm new to this list...
My current project involves transplanting a TBI 4.3 V-6 from a '85 Monte
Carlo (1226868 ECM w/FYW broadcast code) into a '81 Malibu wagon.  The
engine ran great in the Monte, but I'm having some problems in the Malibu.
To start with, I seperated the entire ECM harness from the Monte and swapped
it over into the Malibu.  The engine starts fine, but the CEL stays lit, and
I'm not getting a "pump shot" when I blip the throttle, so the engine bogs
pretty bad.  I can move the TPS lever and nothing happens.  Also, when I
jumped the ALDL to pull the codes there are none set.  I swapped in a
#1228746 / AUML ECM from a '90 Caprice after checking the pin-outs just to
see if my original ECM was bad.  The engine ran, but not very well.  With
the  8746 ECM in place the CEL light went out, and I got a "pump shot" when
I move the TPS lever, so I figured my ECM was bad.  I replaced it with a
re-man unit from Autozone, and I'm getting the EXACT same symptoms.  I did
have a battery charger hooked to the battery while I was checking some of
the power connections to the original ECM.  Is it possible that I may have
fried the EPROM (I had to re-use my original EPROM in the replacement ECM)?
Any help would be greatly appreciated.

Dave
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