So was in the mountain with the family for the past 5 days. Drove up just fine, went to start it the next day and head out for a ride got both of these error code. Would start and idle just fine. As soon as I stepped on the gas it would bog down and start backfiring, no power, could not climb a small hill. Researched and saw it could be a dirty MAF sensor. Cleaned that bad boy, seemed to do ok for a while after. Cleared the codes. Went to leave the next morning, same friggen thing, same codes. So replaced one O2 sensor ( had replaced the other about a month ago) One code went away, still had the other, still running like crap. Replaced the other. Truck seemed to do fine the rest of the day, ran strong. Thought all was good. Went to head home yesterday, popped both codes again and ran like crap again. SO I replaced teh MAF sensor thinking it may just be bad. Did nothing. Took it back to the condo, researched tried a few things, nothing. Left it for a couple hours, went bad out ran just fine and got us down form the moutain with no probblems. Started it this morning, back to the same thing. I can romp on the gas while in neatral and can only get 2500 rpms, with it backfiring.

Needless to say I am at a loss. Any thoughts.

97 GMC K1500 5.7l

 

Just a long shot but maybe a bad fuel filter restricting fuel to the injectors. Were the O2 sensors new? Is your gas good?

 

New fuel flter about a month ago. Both O2 sensors were brand new from NAPA.

 

error code table:Diagnostic Trouble Code (DTC) Table Free Download

 

You didn't mention ignition wires, and that would be my first guess.