1997 Dodge Truck Engine popping

The mechanic replaced the cylinder, plug and wire. When I accelerate the motor makes loud popping noises much like backfiring thru the motor.
He told me this is due to a bad torque convertor.
I originally took the truck in because of what I thought is a bad fuel pump, but the mechanic said the code read a bad cylinder #4. Never checked the fuel pump.
I have to hit the gas tank to get the truck to start.

Thanks so much for hanging in with me !
When I took the truck in to the mechanic it was running very rough. We had already changed the plugs which helped some, but the truck was running really hard, shaking and missing, but not popping thru the intake.
I also put a new battery in right before, so the check engine light did go off for a little while but came back on. I did take the truck thru emissions at this point and it did pass, even though it was running rough and dying at every red light.
The mechanic said the light also went off after repairing the cylinder, but came back on soon as I left the shop.
He test drove it before I picked it up and told me he also heard the popping, hence the transmission was his answer for this. He told me to drive it easy and deal with it.
I have used this guy for years and always trusted him, now I have my doubts.
Since fixing the #4 cylinder, the truck does run alot smoother, almost normal, but, when you accelerate, it does pop thru the intake and loses power like it wants to die. Not something I can live with.
Thanks again for the help.