1994 Dodge Caravan 3.3 loss of power/backfires

I have a 1994 dodge van with a 3.3 engine. It runs fine for about an hour, then once it gets up to operating temp then it backfires through
the intake, spits and sputters and has no acceleration. Recently replaced the fuel pump, new spark plug wires, and coil pack.I tried loosening the gas cap and driving to see if it was possibly vapor locking. The codes we have are 12, 21 and 55. This mostly seems to occur when it sits and gets hot, but the temp gauge doesnt rise, so I dont think it is overheating. It drives fine for awhile and then starts dying. If I shut it off and let it sit for about an hour it goes away. Any ideas of what else to try??
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The 21 is an 02 sensor fault, but wont cause it to die out and shut off, start with checking your fuel pressure. If you loose pressure while driving it will slowly start losing power, backfiring and then could just shut down until the pump cools off. This fuel pump that you said you replaced..........was it an aftermarket pump???
Glenn Beasley Chrysler Tech
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Mine is doing same as the guy above except not throwing coats at all and it sounds like it’s missing now... it sat for 2 months and was fixed and going again any idea what’s wrong
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Try running some good injector cleaner through it.

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replying to wildside1975 , Jerry Mason wrote:

I have the same problem. And did almost the exact same procedures you have done. Now, I have found rainy weather increased the problem and severity. Have your gas tank inspected to see if it is rusting on top or the filler neck is leaking. This will cause water to be splashed into the tank either from above or at the rubber grommet on the filler neck. You will also probably notice excessive fuel consumption.
Water clogs fuel filters. Clogged fuel filters work fine until pressure gets to the point that not enough fuel can be delivered causing hesitation and loss of power. The backfiring is a side effect of this process and is noticeable especially as you press further on the gas pedal and attempt to climb hills. Sometimes the TPS switch can cause this effect, but usually does not correct itself as water in the gas usually does after sitting and cooling. Also MAP sensor causes this surging, so look for cracked and damaged wiring first. A new MAP sensor is about $80.
Try the following steps and see if you improve your situation.
1. Replace your fuel filter first
2. Fill up with good high octane gasoline and add a bottle of injector cleaner or fuel line antifreeze.
3. Repeat additives for the next fuel fill up. The problem should clear up and possible be relieved at this time. Also, if your tank or filler is in bad shape as the age of the vehicle may indicate, I replaced it with a used one because the mechanic could not get a new one to fit the filler tube. You could see gas pour out when half filled.
Good luck. Many mechanics and dealers wanted me to spend thousands and it is only a few hundred including the tank and labor. Finding the fuel filter problem came because replacing the tank also may have caused sediment in the fuel line to exasperate the problem.
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