Car is sputtering and won't start up. on 1990 Plymouth Grand Voyager

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Tried checking the o2 sensor, fuel pump, fuel filter, fuel injections system, did an oil change.
(1) Answer
I have a 94 Plymouth GV LE with 3.8 V6...had transmission problems 2 times...just recently had the sputtering. It acted like it was not getting gas. My friend, an ASE certified mechanic said that if the plugs are not "gapped" properly, it can happen. He changed back to the original factory Champion spark plugs, changed plug wires, put in a new fuel pump(just for precaution) it runs so, so, so much better. Finally, I could take it on the interstate without fear of "stalling out."