o2 sensor

So my 2003 Elantra has been getting horrible gas mileage, running super rich. I had a constant P0420 catalytic emissions code and one misfire reading. I'd clear it and it'd go away for about an hour and come back. I feared I would have to replace my whole exhaust manifold/cat part until I read...

(Can Mod please move to help section of forum. thanks) I had my CEL come on and had autozone check it. they said it was the Bank 1 Sensor 1 O2 Sensor, or the MAF Sensor or an Injector. So I bought a MAF sensor Cleaning Spray and took it to it on the MAF sensor. that removed the code for 3...

Can't believe it! CEL came on today on my way to work. My regular mechanic says the problem is a "faulty upstream O2 sensor". The dealership says the sensors are covered up to 60,000 miles. I've got just over 64,000 miles on my 2005 Elantra! The mechanic wants $270 for parts and labor and...