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Old 01-13-2013, 02:03 PM   #1 (permalink)
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Default 04 MPG is dropping fast

Hi folks,

My 04 2.5mt is having horrendous mileage issues. It needs an air/fuel sensor, which should be here mid-week. Would that be enough to throw off my mileage significantly, or should I look for other issues? Fuel lines etc are good with no leaks, filter is probably due for changing though.

Thanks!
Josh
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Old 01-13-2013, 04:44 PM   #2 (permalink)
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Filter is in the tank.

Mileage?

Where do you buy your gasoline?

Is the engine temperature coming up and staying up? 1/2 way on the temp gauge.
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Old 01-13-2013, 04:54 PM   #3 (permalink)
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Filter is indeed in the tank. Mileage is 156k, gas comes from a small local chain that has always been my choice, so the gas hasn't changed since I got the car. Engine temp is stable.
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Old 01-13-2013, 05:03 PM   #4 (permalink)
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Plugs and wires may be in assistance. The winter blend gasoline is high in oxygenated additives and will make the volume of fuel usage increase since it burns on a lean scale.

Wait and see what happens with the new AF sensor.
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Old 01-13-2013, 05:10 PM   #5 (permalink)
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I would look at the Gas your using 1st, Fed government is allowing 15% alcohol blends now , that can equal about a 20% drop in actual mileage as alcohol is Hygroscopic and readily picks up moisture. Ethanol is not as efficient anyway, but many companies are adding ethanol to reduce production costs, but until recently 10% was the maximum allowable. Ethanol will cause 02 readings to be Lean and your fuel system will be trying to add fuel to compensate for the lean readings. The other significat cause I have seen is a broken retaining clip in the parking brake system or misadjusted rear shoes. This causes drag which can reduce mileage as well.
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Old 01-17-2013, 04:13 PM   #6 (permalink)
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AF sensor is replaced, no more CEL. Gas tank is on empty, so when I fill it tomorrow I'll calculate mileage and see how the next couple tanks go. I will update this thread as necessary for reference purposes.

Joe..... funny you should mention that. I have a seized caliper that is also on order. I found it when attempting to adjust the parking brake. I pulled the pads and cleaned the clips, and while the caliper is still completely screwed, there is no drag on the rotor. I was hoping that would help with the mileage issue, but it did not. I always get gas at the same place. I will ask them about it tomorrow.

Thanks for the input, y'all.

Josh
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Old 01-17-2013, 04:15 PM   #7 (permalink)
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... the fuel filter is in the tank? Did they change that in 04?
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Old 01-17-2013, 04:17 PM   #8 (permalink)
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Yes they did, and I think they went back to the other (better) attachment again in 05, but could be wrong.

In the 04, you have to access the tank from under the rear seat to change the filter.
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Old 01-21-2013, 02:27 PM   #9 (permalink)
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New A/F sensor, cleared code, and 130 miles later got the P0420 code. Ordered a downstream sensor, really hoping the catalytic converter is okay. Can't tell how the mileage is yet, but it's definitely running and idling better with the new A/F sensor. I'll update again in another week or so.
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Old 01-21-2013, 03:12 PM   #10 (permalink)
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Quote:
Originally Posted by ItsJustJosh View Post
Yes they did, and I think they went back to the other (better) attachment again in 05, but could be wrong.

In the 04, you have to access the tank from under the rear seat to change the filter.
My 2004 had just the in-tank filter. I don't think my '08 has one under the hood, either, but I'd have to look again to be sure.

I don't think it's that, seems to me a clogged fuel filter would cause lack of power, not high fuel consumption.
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