1989 Chevrolet pickup/driveability problem

thanks for the response, any answers are appreciated! bad news:
both the pickup coil and magnet have been replaced with known good
parts, same problem!!

I'm looking at a 1989 Chevrolet, 4wd, 5.7 and 5-speed. Here's the
problem: Truck bogs down severely after about half throttle is
applied. At full throttle truck struggles to reach 50mph. Sometimes
accompanied by popping and backfiring. After disconnecting timing
connector under the hood, truck runs much better, about normal. The
only code it will set is when the connector is unplugged. To my
knowledge, the following have been replaced: ECM, distributor, fuel
pump, fuel filter, and most if not all sensors on the engine. I'm
about to check the harness between the ECM and the timing connector.
Does anyone know how to do this in a easy way? Any other ideas on
what to check?

thanks in advance

My Dads Truck did the same and spent a small fortune trying to get it fixed ... He never did get it fixed the engine blew. The funny thing is it wouldnt start bogging down or shimming or anything at times ....it was like something wasnt truely fastened..... Hopefully you can get it fixed and not end up like dads 2001 S-10 did last yr.

Catfish
From Missouri

This is your key right here. The pickup coil drives the EST circuit in
the distributor (or at least part of it). Your problem should be
either in the pickup coil, or the distributor shaft reluctor magnet.
They can get old and crack. When you disconnect the tan/black wire
for the EST, you reduce the current load on the pickup coil and that
is why it runs better. It is then able to handle the current
requirements of the ignition module to run at base timing.

^^^^^^^^^
Why would anyone replace an entire distributor unless the old one has
totally grenaded??? 99% of the time, with this vehicle, the only bad
part is the pickup coil. Some aftermarket rebuilts use the same old
pickup coil and dist shaft. They just clean them up and stuff em back
in...


Mr GoodFish <><