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That 04Sixxer Guy
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I just got 180 miles on a full tank. Everything appears to be fine with the car and it runs just as good as it always has. Oil change not due for another 2000miles, wheels are aligned, normal psi in tires, and driving as granny-like as possible.

I'm thinking O2 sensors because i have had exhaust work done so maybe something happened to one of them? Cars at 79K miles

Could someone tell me what i should check so i can find out why my car could be getting such shitty miles per gallon?

Thanks,
Chris

EDIT: Also tried the full seafoam treatment to no avail
 

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have you changed you're fuel filter in the last 50k miles?

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O2's might be the culprit. Maybe the mass air sensor. If theres no trouble codes being thrown but fuel usage has gone up the car might have an issue that has caused it to go into "safe mode". Not codes will pop up but the computer will retune to ensure that it won't damage anything (by running rich). Theres a number of reasons this might happen but an easy fix is to disconnect the battery, let it sit for about 15 minutes, then reconnect. Sometines that will fix it. I can't explain it any better but my 04 GT did the same thing at one point.
 

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HAHA I just did 2 decent trips. 1 to Vegas and back and another that ran a full tank and I got 23.5 and 24+ mpg. All stock 2002 6er.
 

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HAHA I just did 2 decent trips. 1 to Vegas and back and another that ran a full tank and I got 23.5 and 24+ mpg. All stock 2002 6er.
Oh well that's helpful :tomato


Does the car smell like it's running rich at all?
 

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That 04Sixxer Guy
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Discussion Starter #7
have you changed you're fuel filter in the last 50k miles?
Bought the car 8000 miles ago, so I'm not sure when it was replaced, if ever.

O2's might be the culprit. Maybe the mass air sensor. If theres no trouble codes being thrown but fuel usage has gone up the car might have an issue that has caused it to go into "safe mode". Not codes will pop up but the computer will retune to ensure that it won't damage anything (by running rich). Theres a number of reasons this might happen but an easy fix is to disconnect the battery, let it sit for about 15 minutes, then reconnect. Sometines that will fix it. I can't explain it any better but my 04 GT did the same thing at one point.
Thanks, I'll give that a shot

HAHA I just did 2 decent trips. 1 to Vegas and back and another that ran a full tank and I got 23.5 and 24+ mpg. All stock 2002 6er.
Hey bro, that really helped, thanks...

Does the car smell like it's running rich at all?
Sometimes it does sometimes it doesn't. There's been a few times where I've gotten out of the car to walk inside and smelled gas but never in the cabin
 

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Bought the car 8000 miles ago, so I'm not sure when it was replaced, if ever.



Thanks, I'll give that a shot



Hey bro, that really helped, thanks...



Sometimes it does sometimes it doesn't. There's been a few times where I've gotten out of the car to walk inside and smelled gas but never in the cabin
Could it be the gas tank filler neck gasket? It is a common problem and would explain the smell of gas outside the car. If it were leaking it would really hurt gas mileage big time.
 

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hey OP, i am having the exact same issue, i have already tried sparkplugs and wires that made no difference at all. I dont think im leaking gas, but i do know that taint smell after driving, only once in a while.. But i am going to be trying my O2 sensors and fuel filter either this weekend or next. Ill let you know how that turns out.

I have felt that i have an exhaust leak somewhere, i feel like i hear it sputting every so often when i first start the car, but for the most part it has been running fine. Do you ever notice anything like that? and to others could an exhaust leak cause horrible gas mileage?
 

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hey OP, i am having the exact same issue, i have already tried sparkplugs and wires that made no difference at all. I dont think im leaking gas, but i do know that taint smell after driving, only once in a while.. But i am going to be trying my O2 sensors and fuel filter either this weekend or next. Ill let you know how that turns out.

I have felt that i have an exhaust leak somewhere, i feel like i hear it sputting every so often when i first start the car, but for the most part it has been running fine. Do you ever notice anything like that? and to others could an exhaust leak cause horrible gas mileage?
A vacuum leak or an exhaust leak before the o2 sensors could impact gas mileage.

A vacuum leak will make the computer adjust the long term trim to run richer. The impact of such a leak is biggest at idle and least at WOT. An exhaust leak before the oxygen sensors has a similar effect because the computer sees a lean condition, especially near idle and sets the long term fuel trim richer.

From recent experience I can say that having both vacuum and exhaust leaks can impact gas mileage. The driver's side exhaust manifold gasket was leaking and the windstar intake was not quite seated due to interference with the fuel pressure sensor and cooling system breather vent. Even with both types of leaks, gas mileage was 17 to 20 mph whether you drove the car hard or with care. Also strange was that highway driving was no better than city driving.

There were symptoms. The car hesitated off the line and sounded like it had exhaust and vacuum leaks. You could hear the "hole in the exhaust" sound while accelerating. Under the hood you could hear the hissing of leaks while idling.

13 MPG seems extremely low for a car that has no other symptoms. A fuel leak or "elderly" 02 sensors could explain it. Add a dirty MAF sensor and a vaccum leak from a failed canister purge valve solenoid and you'd be closer. However, 13 MPG is really low.

Has a compression test been done on the engine?
 

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Sorry about how that came across. I wasn't trying to be a dick, just super happy that my 6er finally was getting good gas mileage. Fresh oil, new PROPERLY GAPPED SPARK PLUGS, new tires, new fuel pump, and new !?!?!?!?!? sensor and all was good.
 
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