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Burning A lot of fuel

3826 Views 34 Replies 12 Participants Last post by  citm2000
I'm not extremely car savy but i know the basics. Anyways i have a 2002 GT Eclipse, 39000 miles, K and N cold air intake and custom exhaust. The problem is i burn through SO much fuel. I think i average around 11 miles a gallon. And on start up it spits out a lot of black smoke and there's quite a bit of carbon build up in the tail pipe. So i know that it's not burning all the fuel, i just can't figure out why or how to fix it. I've changed the spark plugs and that didn't help. When i bought the car from the dealer they said that it was chipped but really have no clue if it is. I guess that might be the cause but i don't know where it would be located or how to fix it when i find it. ANy help would be awesome thanks.
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wow pal. sounds like you have a case on your hand.
yeah no kiddin. Can anyone tell me where the computer is located at so i can possibly try to see if it is indeed chipped.

I was also told it was possible it could be the oxygen mixture but i don't know how to test that and really don't want to take it to a shop and pay 100 bucks just to find out what the problem is.

Anyhelp is awesome, this is really burnin a hole in my wallet.
the computer is located in the cabin on the passenger side underneath the dash. If it were an o2 sensor you would certainly have a code.
There are no chips for this car. I don't see how it could be running that rich without throwing a code. Maybe the SES light has been removed? You might want to get it scanned for codes. It sounds like you've lost one or both upstream O2 sensors.
Sorry to steal this thread, but i have some what of the same problem. but i dont want to start a new thread when we can just add to this one.

2002 GT
68,000 miles


I too am burning a lot of fuel, somewhere around 15 mpg. I am not blowing out smoke at all, but i do have build up inside the tailpipe. And i know there is alot because i just put the invidia on about 2-3 weeks ago and just noticed today when i washed the car that its is already built up on the inside. I tried to wipe it away but it is stuck there. i also changed the plugs back in Dec.

and no, im not "chipped" :)
cap and rotor anyone?
nope, have not replaced them or wires, i was planning on it, but have not gotten around to it. Could that really be causing this problem?>
also forgot to add, at start up it sounds like fuel is just being DUMPED in. could this cause a problem as well??
Yeah I would definitely check to see if you are throwing any codes. Also check the MAF sensor, 02 sensors, gaskets, and maybe try some fuel injector cleaner? Also did you gap the spark plugs? Just tossing ideas out there.
start with the basics and go from there. i work at an autoparts store and i tell everyone to go from the little stuff to the big stuff. spark plugs, wires, cap-rotor, coil, also if you are running the cheap gas put in some lucas fuel system cleaner. it will clean out any build up that you have. oh and with the tuneup thing. get the bosch platinum 2 or the bosch iridium plugs because you dont have to gap them. <-- i have them running in my car and they work great.

just some advice..
Any check engine lights?
nope. not one. i even tested the bulb, and its still good.
11-15mpg is about the number everyone reports when their car goes into "gimp/limp mode" (unable to establish closed loop fuel trim control). Still -- in order for that to happen, something MUST throw a code. Juice -- you have something else wrong. Sean -- we need more input.
okay, well after B2N would it help to check the plugs, cap, rotor. And if needed replace. If that does not solve my problem what would be your word of advice. ECU flash, re map fuel trims??? or is anything else i should do first? Fuel injector cleaner, high octane gas, reclean air filter, reset ECU??
Plugs, cap, and rotor can cause poor fuel economy, but usually there are codes associated with misfires that result.

Don't ECU flash unless you've already done that and screwed something up.

You should be using high octane gas anyway.

Fuel injector cleaner is good regular maintenance, but won't fix a problem. Over-use can fry your O2 sensors, especially if they're old. So will those silly octane boosters you can buy in the store.

Don't reset the ECU. Everyone always says this, and it's bad advice. It will just make it take LONGER for your computer to relearn than it will to adjust to current conditions.
juic, if you were closer i'd tell you to bring it to the shop i work at for diagnosis. my boss is really good at it, he'd be able to find the problem and solution, im pretty confident of it.
maybe after B2N i could come down. it only looks like about a 45 min drive. if i get a good deal in a fix, it would be worth it. i dont trust these shops in the city. NOT AT ALL!!! they screw me over on labor rates.
our rate is $85 an hour. diagnosis starts at $85 (less if its really fast to find the problem though), sometimes if its a large repair (lots of $$$) diagnosis is waived IF you buy it. if not then the most you're out is $85 for diag. you can tell us to call you if it seems like its going to take more than an hours worth of diagnosis time to find the problem so that you're not pinned with $$$$ into diagnosising a problem you cant afford to fix right now. we also do a 30 point check on the cars to look for maintence and safety problems. we're big on checking out suspension since these potholes are just tearing shit up.
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