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 doesn’t rise, so I
don’t 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??

 

http://www.autoforumz.com/eform.php?p=614273

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

 

Try running some good injector cleaner through it.