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I have a 97, f150, long bed, reg cab, 6 cyl. Last year I had a "junk yard" engine installed with appoximately 80k miles on it(old one had a cracked block). I initailly got 16mpg. Then it started dropping. I now get 8-10mpg regardless of driving conditions. I was getting codes p0171 and p0174. Here's what I have done: new plugs and wires (twice), new coil pack, new fuel injectors, new egr, new pcv and pvc tube, new fuel filter and system flush, new K&N air filter, cleaned maf sensor, coolant flush, 4 new tires. CEL's are off now. Inspite of all this milage still sucks I need to get at least 3 more years out of this truck. I am probably into this about $4000.00 . Any help/ideas.

 

Try new front O2 sensors. Check for fuel leaks. Check for clogged cats.

 

Discovered problem. My odometer is fluctuating. Sometimes it works sometimes not. So my calculations are correct but my data is way faulty. So any ideas on how to fix odometer???

 

Does the speedometer fluctuate too? If not, I wouldn't worry about it unless you feel like swapping out the whole cluster.

 

If you mean intermitantly going on and off as "fluctuating" it is actually normal. All of these trucks have odometers that turn on and off. It's a bad cold solder point. The odometer actually still counts, just doesn't display it.

 

No, the 97 and 98 have an old school analog odometer, they went digital in 99.

 

It is an old style analog (notdigital). After looking around It seems there may be a worm screw (only cost about $30.00) in there somewhere that is known to break or jam. I am not at all interseted in taking the instrument panel down to fix this. That will probably open up a whole new can of worms. The speedometer is fine though. When I sell it or junk it I'll just report milage is wrong.