I hope someone can help me. I have a '96, 4.9 shortbox with lean fuel codes on both banks (171 and 174) I believe. I have had the truck for about 4 months now. The timing was advanced too high and has been returned to specs, as well as new cap, rotor,plugs, and fuel filter. I have also run about 8 cans of injector cleaner through it. If I delete the codes via the neg. battery method, the truck runs ok the first time out. The second or third drive picks up the codes again and the truck becomes progressively harder to start as well as being pretty sluggish. Any suggestions on how to troubleshoot this problem would be greatly appreciated.

 

1ST CHECK THE FUEL PRESSURE (BOTH TANKS IF EQUIPPED).
ALSO CHANGE FUEL FILTER IF IT HAS BEEN AWHILE.
INSPECT ALL VACUME HOSES FOR CRACKS, GOOD CONNECTIONS, ETC. I JUST HAD THE SAME CODES AND MY FUEL PRESSURE WAS LOW ON MY FRONT TANK, REPLACED PUMP AND FINE NOW.