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Discussion Starter #1
2003 Lancer OZ edition, 4G94 Engine, only mod I got is a K&N intake, which originally gave me around 20 miles more per full tank of gas. Things were splendid. Lately, for some reason, my gas mileage has been losing... Draastically. Like most people, I record my gas mileage. When I fill up, I reset the odometer, and see what I get for each tank. When the gas light comes on, I'm at about 315-320 miles. Always in there, less if I drive like a jackass (which I dont) more if I drive solely highway (which I occasionally do). Now, out of nowhere, I'm looking at 250 miles on a tank when the light comes on! This has happened on the last few tanks. Since it started happening, it has stayed like that. I'm looking at 20 mpg on my Lancer. My dad got the same gas mileage on his 02 Mustang GT. With an engine more than twice the size of mine. I figured that it was a dirty air filter. So, I got the recharge kit, and, following the directions to the T, cleaned the hell out of my air filter, reoiled it, and re-attached it. A small power increase with the clean filter, but, still the same mileage. I'm getting up there in the miles, 95K, and, like was told to me a while ago, things would start failing around 100K. I'm not hugely mechanically inclined, so I only know of a few things that would affect gas mileage. I have my tired properly inflated, clean air filter, and I drive as economically as I possibly can. I've put in fuel injector cleaner, yet still nothing. My front O2 sensor is broken, has been for a long long time. I was still getting excellent mileage before with my busted O2 sensor, so, as far as I know, it cant be that which is causing the horrific change in mileage. Might it be the belts? They are a little bit loose, can hear small amounts of ringing at idle or slow speeds, cant hear it at higher speeds. My car seems to be running fine otherwise. It goes, dosent idle rough, that I know of, and goes well. Granted, I do only city driving, but I've been doing only city driving for quite a while, since well before my gas mileage started lacking. I dont fill up with crappy gas, I know that can mess things up, so I stick with Hess/Mobil/Shell/etc... Any ideas on what to do? I'm in school, so I cant afford to bring it to a mechanic to have it checked out. Mechanics can also smell a mile away when someone dosent know about cars, and would exploit that fully.

Anyone have any ideas? This is coming at a very inconvenient time, seeing as how gas prices are skyrocketing. It would be a huge help if you guys could help me figure this one out.

Anything else you need to know, tell me.

Thanks again fellas!
 

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Discussion Starter #3
Boots come with the wire set? Anything else I should do? Got a recommendation on what plugs I should use?
 

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also replace the fuel fillter
and alway go with the stock recomended plugs unless you've modded the motor
you always get the best mileage out of them or well at least in my experience
 

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ok well first thing you need to do is get a new O2 sensor, i was getting crappy mileage for a while, then i replaced the sensor and it was fine

put some seafoam in with your gas next time you fill up, and also put some in with your next oil change.
Get some throttlebody cleaner and clean out your intake manifold, also pull off your EGR valve and clean it out with throttle body cleaner.

Replace your plugs and ignition wires. NGK's are the best

Do all of that and you should get your mileage back
 

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Discussion Starter #7
So I re-did my plugs, wires, and o2 sensor, and things were looking up on my first take of gas thereafter. There was a noticeable difference in the idle, though, it idles lower than I ever knew it could. Dosent make any noise or shake, thats swell. But this tank of gas is already looking bad. 60 miles on a quarter of a tank? Not cool. Havent yet gotten the Seafoam, I'm going to try to grab some of it today if I can.

Would you happen to know where my EGR is? I have an 03 Lancer, with the 4G94 engine. I'm new at the whole mechanical aspect of cars, bear with me.

Can you tell me where the fuel filter is?
 

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See attached for the EGR valve.

The fuel filter integrated into the fuel pump, which is located underneath the rear seat. I cannot verify this because my online repair manual does not give me that information. I would not change it yourself (if you're new to the mechanical aspects of cars).
 

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your fuel filter is just a gauze type deal built into the fuel pump i believe. Here are pics of the EGR valve location and the screws to remove it:

careful when cleaning it though. Only use throttle body cleaner. If the EGR valve gets damaged your car will run like crap.

also 60 miles at a quater isn't to bad. i think i get about 70-80. you gotta remember that the lancer fuel gauge isn't exactly precise, it may read a quarter of a tank, but that doesn't mean its at a quarter










 

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Discussion Starter #10
Hugely appreciate the pictures. But one thing at a time. I'm at school right now, so I dont think I have the time to take that off and clean it. But vacation is coming up soon, so I'll get down to it then.

Just picked up some Seafoam, going to run it into my oil and gas. I did some reading on it, and apparently I can also put it through my throttle body (or vacuum lines) and it'll clean the hell out of those. I'm a little apprehensive to do that. For one, I'm not sure how to do it. Can someone tell or show me? Does my vacuum line feed to all cylinders? I'm new to this, but theres only one way to learn. Gotta jump in head first. I also read that I should change my spark plugs shortly after using Seafoam. Why? Is it really necessary? I just changed them like 400 miles ago (if that). I watched a video of a guy who had just put some into his throttle body, all that smoke coming out the exhaust for a few minutes... It looked like stuff was getting done. Someone maybe want to give me a little step through on how to do that?

I'm really curious, and very upset, at my gas mileage. I know you said the gas meter isnt always correct, but when the light comes on, and I fill it up, it's always the same (10-11 gallons go in). When I did the tune up (plugs, wires, o2 sensor) my idle lowed drastically, and for the first tank of gas, my mileage was better (not back to normal, just better) but now it seems that it's back to being just as bad as it was... Perhaps, dare I say, worse. Is there really anything else that might be causing this? Its getting bad, I'm looking at 15-20mpg on my Lancer. My buddy gets better gas mileage on his 12 year old Explorer thats in hell shape.

All is appreciated

Thanks again
-Tyler

EDIT: Went out and looked under the hood, put some things into perspective. Found the EGR, but that entails taking off my strut bar and intake and alot of time, none of which I can do right now, so that'll have to wait until I go home in a few weeks (unfortunately). Pretty sure I found the throttle body (the throttle cable connected to it, so I'm asuming) it's got two hoses on it, not sure which one to use for my Seafoam. Someone tell me?
 

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also replace the fuel fillter
and alway go with the stock recomended plugs unless you've modded the motor
you always get the best mileage out of them or well at least in my experience
Hey where would one find that fuel filter on an 03 oz rally lancer? Can't find much good info online
 
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