i went to the mechanic the other day for the CEL and they told that my knock and O2 sensors were bad and needed to be replaced.. would these two things contribute to my gas mileage to drop? i get about 200 a tank right now.. they also told me that a tune up will raise my MPG significantly.. need help!!!

 

Yes on all counts, and use the search. There is a ton of information available on here as far as knock and O2 sensors, and the replacement procedures. If you don't want to install the parts yourself, buy them online and bring them to the mechanic to save some money. Knock sensor will be about $60 on ebay, and O2 sensors can be bought for reasonable prices at www.oxygensensors.com

 

change ur spark plugs fuel filter air filter knock sensor o2 sensor ur pcv valve you do all this your gass milage should go up a good 60 more miles a tank AND if you do all of this yourself and you can easy ( exept the sensors if you get the universal ) would cost you about 200 bucks and the car will run much better

 

As Crime said, knock and O2 sensors are biggies when it comes to gas mileage. A full tune will help as well. Maybe not as much, but it will help. Buy a Hayne's manual and get busy!

 

Always DIY. Weather its a Bad Starter or Windshield Wipers. Do-It-Yourself.
Not only is it Cheaper, your also learning a valuable skill!

Oh and guys did we fail to mention the Knock Sensor MIGHT be a Ghost Code?