skierd

<div class='quotetop'>QUOTE (silvertibbs)</div><div class='quotemain'>Yeah, normally that happens, your car kinda gets used to running at a certain level. Then when you return it to stock or better, it doesn't like it. I'd have to agree with skierd here and say that an 02 sensor is to blame. You could be running hella rich and it should throw a CEL.</div>

Should. What I think happens is as the sensor fails or gets clogged, it consistently reads less and less oxygen, which then tells the ecm to run richer and richer. Its a cycle that has to get pretty bad for the car to throw a CEL.

majik

nice to see you around here skierd... welcome.

how many tanks has this bad gas mileage been going on? No CEL? I was thinking of a major leak somewhere in the exhaust or intake. Do you have a factory air box intake system still on your engine?

hyundaipower

<div class='quotetop'>QUOTE (majiktib)</div><div class='quotemain'>nice to see you around here skierd... welcome.

how many tanks has this bad gas mileage been going on? No CEL? I was thinking of a major leak somewhere in the exhaust or intake. Do you have a factory air box intake system still on your engine?</div>

this has been going on for about 5 or 6 tanks. i did get a CEL only after i did the E-clean, but i read and erased the code.... it was a cylinder4 misfire, which is normal for a E-clean. i do have a exhaust leak, but i have had it since i got the car 1 1/2 years ago, so i dont think that is it unless it is getting bigger fast. and i have a stock air intake, i have no engine work done...yet smile.gif

majik

I know for a fact that some exhaust leaks can cause your car to lose up to 50HP. My friend did a dyno at two car shows, one with an exhaust leak and one without. He has about a 45hp gain after it was fixed.

I would suggest getting a Cold Air Intake for the car and getting that exhaust leak fixed (buy headers and a cat-back exhaust)... it'd be cheaper than replacing it with factory parts and having the dealership fix it (unless they'll warranty it). I'd go to AutoZone or somewhere and ask them to read the codes (maybe it will still show a CEL code). You said you had a recent tune-up... I'm assuming you've replaced the spark plugs and wires, right?

Can you relate your drop in gas mileage to any specific thing you did to the car? (immediately after tune up, or changing the air filter, or anything else?)

hyundaipower

i changed the plugs and wires when i did the tune up. i did not do anything immediately after the the tune up to the car at all. im gunna try the O2 sensor, and fix the leak, and if that doesnt work, i have no idea. thanks for all the help.

Slipstream

what octaine fuel are you trying to run? any additives? do you smell gas at all when you get in the car or drive? you could have a faulty injector as well.

zhiryst

I'll bet $500 monopoly dollars that it's the fuel filter. Try that first, it's cheaper than the o2 sensor.

Dweet

im goingwith skierd and saying replace your fuel filter and your O2 sensor BEFORE the cat