Hi everyone I just got a 91 S10 blazer 4 by 4 with a 4.3 auto. The
motor came out of a astro van and it idles fine up to 3 mins or so and
then drops down on idle and then it either dies or comes back up.
There is no trouble codes that come up. It also does it in gear. I
don't have a clue what it might be. Other then maybe a fuel problem or
a pickup coil. If you slowly press on the pedal it goes up just fine.
If you floor it it 1/4 of the way down then it falls flat on it face
in park or any gear and then it dies or comes back up. Any idea's???
I'm just completely lost and don't know what to do. Thanks for your
help and idea's that you can give me.

It sounds like a bad fuel pump, or clogged fuel filter.

IS IT TBI OR FUEL INJECTED? IT SOUNDS LIKE YOU MAY WANT TO CHECK OUT YOUR FUEL
FILTER, BUT ALSO CHECK YOUR PLUGS AND ROTOR, AS IT SOUNDS LIKE IT'S NOT BURNING
THE FUEL FAST ENOUGH WHEN YOU FLOOR IT. ALSO CHECK YOUR CHOKE.

Pat

CHECK YOUR PLUGS AND WIRES, IF YOU HAVEN'T CHANGED THEM IN A WHILE, IT MIGHT BE
A CRUDDED UP PLUG. CHECK YOUR FUEL PUMP TOO, IF YOU CAN.(MINE IS RIGHT UP BY THE
FRONT OF THE STEERING COLUMN). IT MIGHT ALSO BE YOUR EVAP CANNISTER THAT MIGHT
BE GUNKED UP. THROW SOME HEET INTO YOUR TANK AND SEE IF THAT HELPS TOO.

Bob

Is your filter in the right way? Check your egr valve,
unhook it if ya want. If you still have your old
engine swap your tbi assembly and egr over, knock
senser 2 maybe. Try new injectors last. Good luck

Hey everyone. Thank you all for giving me idea's on what it was.I
did swap the tbi back and now it works just fine. I would have never
known about doing that before until now. So thank you everyone.