Thanks alot man, i just looked at that website. Going to order me both OEM o2 and see if that fixes the prob

 

maybe you have a bad O2 sensor. something is wrong you should take it in and get it checked out.

 

Sorry I didn't read the rest of the post you already know about the O2

 

Would COP along with new filter, plugs, maf help?

 

8ES a little cold for running a stock setup. im not an expert on the whole spark thing but 7es should do plenty good enough. champions :facepalm: its not a lawnmower

if it was the maf you would hear it and the car would struggle to idle.
clean the injectors while your at seems your doing a full tune up anyway.

 

I really didn't use boost once! Otherwise i would have gotten less than 200 miles out of a full tank.

 

this thread is funny ... lots of funny things said .. so your the one ive been stealing gas from...lol my bad lol... but really change all these things im also interested in knowing what fixed all or most of this problem. what about retuning your car? i mean what if before you the owner had all kinds of mods in this car then put it all stock before he sold the car back? couldnt this have anything to do with your mpg and all?

 

Sounds like your getting 9 miles to the gallon.
You know the fq400 gets 9 miles to the gallon, are you driving a stock fq400?

I see more and more cars being sold as stock, guys put everything back but never flash it back.
new EVO owners beware!

 

^ This. Or a boost leak.. Im running E85 at 28psi and getting better mileage than that..

 

I have been reading tanman's other threads and there is def something going on with the car. Im fairly certain its gonna show up in the boost leak test. When you have a boost leak the car goes rich because it is metering more air than is actually entering the engine. I have a fairly small boost leak ATM ( too lazy to mess with cuz im worken on other ppl's cars at the moment) but as soon as the car crosses into boost to get up a hill or something the wideband pegs rich.

Also just because your car is stock doesn't mean it was. tons of evos get de-modded when they are sold or traded in and id bet 8-10 still have the tune from when they had all the aftermarket stuff on.

 

I get about 150-200 on a tank. And thats on e85.

When i was on pump, i got around 230-260. Most i ever saw on a tank was 335.

 

I consistently get 240-250 a tank even with a bit of boosting. I would just do a complete tune up (oil, oil filter, air filter, spark plugs and o2 sensors) this will eliminate the maintenance portion of what your car needs for the basics. Also even if your maf doesn't look dirty still clean it anyways and there can be some build up on it. My car was running fine and I cleaned the maf and it was disgusting.

Do you have a wideband installed( I read the thread and saw no mention of one)?

 

E85 decreases gas mileage.

 

e85 decreases fuel mileage a good bit since e85 has less energy then gasoline

 

OP, don't listen to 90% of what ppl say here. Most of them are completely wrong, even though their intentions are good. You will save money in the long run by taking it to a reputable shop that can diagnose the issue for you. If you do decide to throw an O2 sensor in it, just replace the one in the O2 housing right below the turbo....the one in the cat will not affect your fuel mileage. The MAF sensor can also reduce your fuel mileage, but you would most likely notice other driveability issues. Personally, I would vote for a leak in your intake manifold between the throttle body and the head. This will cause a high idle and set the code you are getting. Since there is extra air entering the engine, extra fuel will be added to compensate, and reduce your mileage. But like I said, you will most likely save money in the long run having it diagnosed properly.