Okay guys, i'm new here, didn't see anything on this so I figured I would ask. I have a '97 1500 4WD sport. Odometer is showing 220k or so, but the guy I bought it from said that the previous owner did a motor and trans swap but he was never given paperwok on it so I can't verify that. Motor runs fine for the most part other than needing a rear main seal. The only problem I have with it is when I start it up, and start going, whether it sits or not, the motor will bog down and start knocking. If, once it starts, I get into it and run the RPMs up it will stop and run fine from then on, but once I shut it off again, it will do it again. Have done the plenum gasket, basic tune up stuff, and the like, but can't seem to figure it out. It doesn't throw any codes and the motor runs smooth otherwise. Thanks for the help.

 

Sounds like a fuel issue,either loss of pressure or a injector leaking,before you start the engine open the Schrader valve on the fuel rail and see if it has pressure,if not it can only be 3 different problems
1.injector o ring
2.fuel regulator bad
3.fuel pump in tank has a check ball
Or a stuck injector dumping to much fuel,run a can of sea foam in fuel