mileage swing

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Feb 2, 2007 | 07:58 PM

Guest

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mileage swing

I did a search for gas mileage but didn't get anything that seems to fit my problem. I've got a 03 X-type 2.5, my check enging light keeps coming on, I go to my mechanic, he reads it and then clears it.Within 15-20 miles it comes back on. All the codes ever read is that it is too lean. This has been going on now for 6 to 8 weeks. I've changed the oil and filter, I've changed the air filter, and the fuel filter. Any ideas on this. Alsoabout everyother tank of gas my mileage swing over 10 to 12 miles per gallon. This last fill up I only got 17.5 mpg while the one beofre it I got 29.3. I only drive 25 miles a day round trip to work. No change in type, all city, speeds under 50 mph with 7 stops atlights/stop signs, temps run for mid 30's in the morning on the way to work and mid 50's on the way home. Anyone have any ideas on the swing in milage? Could the fact that the car was originally from Florida and I bought it here (El Paso) used,have anythnig to do with this (my elevationhere is 4000 ft +/- 20', while in Florida it was at sea level). And finally, sometimes, not alway, when it is shifting from 2nd to 3rd and occationally from 3rd to 4th it will almost die, I mean the engine goes flat, no power but it doesn't stall. Any help would be nice.

Thanks

Feb 2, 2007 | 09:38 PM

racerx82

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Joined: Jun 2005

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Likes: 13

RE: mileage swing

Well first off, what was the code # and why didn't "your" mechanic investigate it further? If the code is cleared and returns after a few days, or few miles, that means the computer stored a hard fault and you should be able to read the code and start your diagnose from there......(the reason why the computer is telling you this so you don't have to play hide and seek in guessing what to replace)

ANYWAY...if it's reading a lean condition it's most likely one of the 2 oxygen sensors. Left or right...I would replace both...and start from there...one bad oxygen sensor will cause the poor fuel milage you describe...when the sensor is working, you get the better fuel milage......

If your mechanic wasn't able to figure that out or didn't explain it to you correctly, i would find another mechanic....fast

Feb 3, 2007 | 03:33 AM

andersen06

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RE: mileage swing

Right On!!

Feb 4, 2007 | 02:20 AM

bojangles

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RE: mileage swing

LEAN means too little fuel... and yetyour mileage had gotten worse ..... so how does the mechanic explain that???? and how did you drive away after paying him ??? seems all too odd to me..!! Did i miss something more basic than that? do you leave a trail of bills so you can find your way home?

"I've changed the oil and filter, I've changed the air filter, and the fuel filter" sc

I mean how do any of these fix a lean condition? THis is an internet message board.. I can only help based on what you write.

B

Feb 4, 2007 | 01:57 PM

racerx82

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Joined: Jun 2005

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Likes: 13

RE: mileage swing

A lean condition is when your engine does not receive enough fuel for a PROPER combustion. Hence the oxygen sensor determines whether your engine is running lean or rich and makes the proper adjustments...
Lean condition will "burn" holes in your piston and or burn out your valves, also, a engine running lean will run hotter, creating more problems with in the cooling system and burning out your cats....easy fix...check oxygen sensors, fuel filter and use only fuel octane rated for your engine. A lean engine can actually seize.

The opposite of that is an engine running rich....meaning too much fuel and not enough air. Running rich will also decrease your engines performance level giving you poor fuel economy, black smoke out the tail pipe and possibly clogging your cats. How will too much fuel give you poor performance? Easy, your combustion chamber gets too much fuel and doesn't have time to burn it all in the power stroke...actually decreasing performance and wasting fuel. (An occasional backfire will let you know you have fuel sitting in the mufflers waiting too explode) Easy fix, check oxygen sensors, fuel injectors may not be misting fuel properly, air filter, and change oil once you have fixed the problem,

The sensors, hence the name "oxygen sensors" sense the amount of oxygen coming out of the exhaust via the heat generated and read in volts.
A properly running engine will run a bit lean to give to your the proper fuel economy, performance and smooth running engine. If one of those is offset then it will greatly effect the others...anyway, this is only a tip of the ice berg, there is more to this system and how the computers control your fuel system....and how everything works.....so if you're not sure and your mechanic can't fix it...like I said, find another one fast...