facutvivo

bought my 4.9L 6cyl eddie bauer new, installed 3.73 ring/pinion and pulled a small 5WT for years. vehicle now at 131,000 and running very sluggish with engine code 0171 or 0174 I can't recall which. I replaced plugs, wires, cap, rotor but not fuel filter. not much improvement, so I replaced fuel filter one evening and immediately when I started up the truck it ran awesome. I was amazed. I squealed tires easily and next morning looked forward to driving my "new" truck to work, but it ran like s**t again and engine light back on. Driving around town, stop then restart after 10 minutes it starts very hard, knocks, etc. Why did truck run SOOO well right after fuel filter replaced, but then bad again? Oxygen sensor? Bottom line I'm hoping for some suggestions to get my truck back in better running condition. Thanks for the help.

Pat
Roseville, CA

Fast Hampster

Welcome to the forum! Do a fuel pressure check, it will help to figure out what's going on. You also have a filter inside of (each) tank, it might also be the cause. Of ther possible cause is that when you've replaced your fuel filter, it increased the fuel flow (like it should) along with dirt flow (like it shouldn't), so it is possible that fuel system is clogged up again. If fuel pressure test will show low fuel pressure, you may want to apply some fyel system cleaner to fuel tank and drive for a couple hours non-stop. It might help.

facutvivo

sprayed the MAF sensor with CRC MAF sensor cleaner and it has made a huuge difference. I can spin the tires in 1st gear which I haven't been able to do cause it has run so sluggish. I will add some injector cleaner to each tank when the fuel is low, before fillup.

bobstrixx

Try some stuff called seafoam. It's some real strong stuff for injector cleaning.