I recently bought a 96 f-150xl 4.9l inline 6 with about 183k miles. I drove it for a few days and now i have a check engine light with codes p0171, p0174, and p0420. The truck has been driving fine as far as i can tell. No problems with hesitation or engine sounds. I am due for a emissions inspection in a month and need to get this fixed. Any help would be appriciated
171 and 174 set together usually point to MAF sensor or fuel pump. If it's running okay i wouldn't worry about it, to pass inspections is a different story.
I would recommend pulling the pigtail off your maf and spraying some electrical contact cleaner in the sensor connector and also the pigtail to make sure the connection is good, and then erase your codes with your scanner (or go to your local autozone and get them erased for free).
If that doesn't help, you can buy a can of MAF cleaner for about $10 and try to clean the MAF element itself. If that doesn't work, you could attempt to replace the MAF sensor, usually about $100 and about 5 minutes to replace.
But it could also be a fuel issue or a vacuum leak. When MAF sensors go bad, you tend to get hesitation when accelerating or 'bucking' while driving.
If you find the right people at your local auto parts store, they may be able to let you 'try' a new MAF and return it if it's not the problem.
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