My 94 ram with 268,000 miles started pop and backfire. about a year ago plugs, cap, wires, rotor, coil, fuel pump, were replaced. Changed out crank sensor with a good used one, still does same thing. It will idle and rev in park but under load, any throttle past quarter or so and almost to wide open it backfires and pops and wont pull itself. At wide open throttle runs fine and til about quarter throttle. I am thinking throttle position sensor or pickup under distributor cap. Any other ideas before I start buying parts? Ever happen to anyone else?

What do the codes say?

sounds like a valve train problem to me. Worn out cam?

did you ever retime the base timing, did you ever replace timing chain? id do those first

what ever manifold its backfiring through,intake/exhaust...ck the valvetrain there,bent p/rods,broken springs,valve leakage,ect...or t/chain just jumped. also a comp ck might find the issue too.did you get it hot? valves wont seat after a overheat,and or cracked cyl head.

I would try hooking it up to a scanner to find out what's happening before you throw parts at it. Could be a bad O2 sensor. Sometimes the Magnum intake plenum cover gasket can blow out and cause pinging and excessive oil use. It creates a lean condition, so it could probably also cause popping/backfire.

Never got hot, it not only backfires it doesnt run. almost quits til i let off, then it takes off. If i give it just enough gas to drive its fine, give it a little more and it surges, then a little more and backfires and pops, put it to the floor and it takes off like nothing is wrong, revs up to 5500.

I'd check the plug wires after dark for cross firing. I know you put a new set on a year ago but some new stuff isn't all that great. Plus it won't cost you anything to look for sparks. Maybe even mist some water on 'em. Might check the cap for carbon tracking too.

Are you positive of good fuel pressure and flow?

id look at the 02s sounds like its shorted to voltage, and the pcm is making it lean

I checked fuel pressure, had 45psi, not sure on flow itself, how do i check voltage on 02 sensors?