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Gas Mileage Drop after fuel filter???

kifferarri

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By disconnecting the battery, you will be clearing the trucks "learned memory" on how it should run. It will reset to a factory default, and very quickly relearn. If you do not do that, it can take a VEEEEERRRRRY long time to change, and relearn new parameters. After doing a fuel filter, there is always a chance that you may have changed the way fuel is getting to the engine, and therefore changed the fuel trims. A very common practice at the time of doing tune-ups (plugs, fuel filter, fuel injector system cleaners) is to use the scan tool, and reset the KAM (Keep Alive Memory, or "learned memory) and allow the computer to quickly relearn, and run properly with proper fuel trims (improving gas mileage).
Now I'm not saying this is the silver bullet your looking for, but it also would not hurt. If you have access to a scan tool, I suggest clearing the KAM. If not, you can disconnect the battery for a few minutes, and that will clear the KAM. (As suggested by esclamada and number4)

Another point from your last post, timing chains can/do/will definitely have an impact on EFI. Being out one tooth one way can cause a lack of power due to timing being over retarded, or have horrible fuel mileage due to being over advanced. Just another piece of food for thought.
 



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Ourobos

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I've reset the battery multiple times, if that clears KAM then it should have been cleared long ago. As a matter of fact, replacing the battery is the reason my 4x4cm was killed and needed replacing, a brilliant design on the 2002s by Ford. Just for perspective, the fuel filter mpg change was this past spring, well over 7-8k driven with crappy mileage since then, I just did the timing chains last month, about 400 miles ago, so I don't think it's related. Thanks for the ideas though. I'll see if my buddy who owns a NICE (expensive) snap on scanner can read the deeper codes if there).
 






pet575

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There is a difference between disconnecting the battery and completely resetting/clearing the capacitors for the PCM and related components. Take a look through the recent threads-there is one in there on how to clear them.
 






Ourobos

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Yeah.. I've reset similar to the posts on here's instructions.. I just did it again to be safe, I'll monitor my trip tomorrow.
 






Ourobos

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Well, after my purely high trip, it's getting 14mpg highway, and about 11 city.. So that about a 3-4 mpg drop on average.. About $1000 a year.. My advice for anyone who plans on changing your fuel filter as routine maintenance, DON'T.. Don't touch it unless you have a lean condition on your CEL.. Going to try a ECT sensor next, hell what's $20 more bucks.
 






Aceallways

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Well, after my purely high trip, it's getting 14mpg highway, and about 11 city.. So that about a 3-4 mpg drop on average.. About $1000 a year.. My advice for anyone who plans on changing your fuel filter as routine maintenance, DON'T.. Don't touch it unless you have a lean condition on your CEL.. Going to try a ECT sensor next, hell what's $20 more bucks.

When I changed my fuel filter I went from 12mpg to 15mpg mixed so I would give everyone the opposite advice.
 






swshawaii

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My advice for anyone who plans on changing your fuel filter as routine maintenance, DON'T.. Don't touch it unless you have a lean condition on your CEL..
Brilliant advice. :confused:
 






Ourobos

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Go for it smart guys. Only item changed before my immediate fuel economy drop. If it's not broke don't fix it. Except for you two geniuses of course.
 






Gatorblazer

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What would it hurt to change it again and see if that makes a difference? $10 spent to potentially save $1000 might be a good play
 






swshawaii

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If it's not broke don't fix it.
Today I used some MAF cleaner and did the air box mod putting some 1" holes in the box to get more air into it. Still no change.
Was your air box broken? I'll bet 99.9% of the people here won't follow your fuel filter "advice" with good reason.
 






Ourobos

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Guess I should have spend $370 for a cold air intake? That's probably you're rational. Buddy, I've built over 150 EFI Fords from the ground up, and your trivial opinion means nothing to me. I bet you're the .1%.. All the emperical evidence points to replacing the filter led to worst fuel economy.. Do whatever you want, it's a free country, you're welcome for that.

This thread isn't here for your stupidity, if you don't have anything useful to say, stay out of it.
 






Ourobos

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What would it hurt to change it again and see if that makes a difference? $10 spent to potentially save $1000 might be a good play

Hmm.. I might do that. I went ahead and picked up a ECT sensor, 155k on the engine, so it is probably had it's use, going to see if that makes any difference first, if not, I'll try that again, thanks.
 






Limited02

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Go for it smart guys. Only item changed before my immediate fuel economy drop. If it's not broke don't fix it. Except for you two geniuses of course.

I've changed the fuel filter in my Explorer several times (as well my other cars) and not once have I seen a drop in mpg. Either you have a faulty fuel filter that would be worth replacing again, or something else gave out at the same time you replaced the fuel filter.
 






Ourobos

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Sounds feasible, thanks. Will do ECT then filter in a few days and update.
 






Ourobos

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Well, I decided to return the temp sensor, as I didn't think that was the problem. Went ahead and grabbed a new $20 fuel filter. Removed my old filter, noted 'Made in China', I guess I cheaped out on it last year. I also was reminded why I didn't enjoy changing it.. Hard to get to, TWO inlets, one outlet (can't put it on backwards FYI), and the clips were a bear, pop open, press out from bottom with limited space.. BUT anyways.. Put the new filter on, drove through town, traffic, more of a pure stop and go city drive. Got back home, was reading 15.0 MPG.. Back to normal it seems.. Who would have thought a new fuel filter was faulty or just crappy in general? Apparently two of you did anyways.. Thanks guys, I'll report back after my next highway trip and let you know if I'm back up above 17 MPG highway.
 






Limited02

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Well, I decided to return the temp sensor, as I didn't think that was the problem. Went ahead and grabbed a new $20 fuel filter. Removed my old filter, noted 'Made in China', I guess I cheaped out on it last year. I also was reminded why I didn't enjoy changing it.. Hard to get to, TWO inlets, one outlet (can't put it on backwards FYI), and the clips were a bear, pop open, press out from bottom with limited space.. BUT anyways.. Put the new filter on, drove through town, traffic, more of a pure stop and go city drive. Got back home, was reading 15.0 MPG.. Back to normal it seems.. Who would have thought a new fuel filter was faulty or just crappy in general? Apparently two of you did anyways.. Thanks guys, I'll report back after my next highway trip and let you know if I'm back up above 17 MPG highway.

Good to hear it's getting back to normal :thumbsup:
 






zpn_by

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Guess I'll try that too once it warms up. I actually experienced the same thing as the OP - a noticeable drop in MPG after changing ONLY the fuel filter. I replaced it with a genuine Ford part (was working at the dealership at the time) and I was amazed that the MPG dropped and hasn't really ever recovered. That said, I still get 19-20 MPG on the highway, but a dismal 11-12 in the city. Don't even get me started on current MPG - I'm somewhere around 10 right now but that's due to the extreme cold we've been having. Unfortunately my Ford is parked on weekends and we use my wife's RAV4 (still a decently fun alternative). I'm glad to hear your second fuel filter helped the situation - I'll likely give it a shot in the spring.
 






Ourobos

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Drove a 300 mile highway trip today, pulled my utility trailer the whole way, still managed 14 mpg. I think it would have been above 16 without the trailer. Good luck in the spring when you change yours.
 






blackout881

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My 04 gets maybe 16 highway and 9-10 city right now in the upstate ny winter. During the summer it will get 18 or so highway and 11 city. 6 years ago when I got it it got 21mpg highway in the summer and 15 city.

Im upset with the decline in gas mileage, but the truck is 10 years old. Its been there for me when I needed it, and it still runs great.

So the best decision here would be deal with the gas mileage decrease instead of throwing tons of money into it. Treat yourself to a nice dinner.

I am 26, I don't run as fast as when i was 16. My knees hurt. Your explorers knees hurt a bit.
 



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Ourobos

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Have you changed your fuel filter lately blackout? Might return you to those 20 something memories of 21mpg. Go with a quality filter is what I learned.
 






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