[Diy_efi] More 4.3L TBI Timing Issues update

[David Daniel]

David,
I spent several hours last night tracing wiring on the Malibu.  First I
checked for continuity to ground on all four wires in the four wire plug at
the distributor.  3 of the four were open, but the 4th wire (the white one)
that leads to pin D4 was a reading of 8.0 on the 20K ohm scale.  That was
with the key on, engine off, and with the ECM plugged in.  With the key off
I get a reading of 1.6 on the same 20K ohm scale.  When I unplug the ECM
that reading goes away and I get an open circuit reading.  The four wires do
not short to each other, either.  I checked every possible combination for
continuity with each other and got open reading all around.  I also checked
the small harness that goes from the coil to the two wire connector on the
module.  It checked out good.  I unplugged the ECM and checked for shorts to
ground on the four wire connector.  All four read open, so the white wire
must be grounding inside the ECM through a chip or resistor.  While I had
the ECM unplugged, I checked for continuity on the four wire connector and
all read fine, the tan/black wire included.  I checked the power and ground
connections at the ECM as well.  All grounds check out fine, battery wires
have 12v at all times, and the ignition connections have 12v only when the
key is on, just as they should.  All of the wiring seemed to check out fine.

If the weather permits, I'm going to throw the laptop into the Malibu and
fire up WinALDL and try to make some sense of what I see there.  I may even
pull the ECM out of my '88 S-10 and put the ECM I'm running in the Malibu in
it and see what it does.  If the S-10 runs fine then I'll know for sure that
the problem is in either the wiring or a sensor.  I'm not sure what else to
do at this point.  I pulled my S-10 into the garage tonight and unplugged
the tan/blk wire...engine RPM's dropped and the CEL came on, just like it
should.

I'm going to ask a friend to come over and give me a hand with this.  He's
an electronics tech in the Navy, so he should be a great second set of eyes.

I'll post more when I know more...

Thanks again,
Dave
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