Mitsubishi Repair: 03 eclipse sensor, differential pressure sensor, mileage check

Question
I recently bought an 03 eclipse gs. Has about 135k miles. The check engine
light was on but I never paid any mind to it. Although its a 2.4L 4 cylinder, I
always felt it wasnt giving me great fuel consumption. A friend gave me the
exhaust off of his eclipse when he totaled his and I put it on. Consumption
got worse. I got an air intake on it, again consumption got much much worse!
The guys at autozone said my o2 sensor at bank 1 sensor 1 was faulty. Also
they said the manifold differential pressure sensor was faulty. I got the o2
sensor for 115 bucks though I'm broke but I'd be more broke if I kept burning
all that gas. I havent put on the o2 sensor yet. I'm not exactly rich so I'm
afraid of coming up with a huge bill. Will the o2 sensor help? What the heck
is a mdp sensor, what does it do? Any effect on consumption? WHAT DO I
DO?????? Help please.... And some good news if u don't mind, thanks!

Answer
Sharuk: Oh yes you change those 02 sensors and that would help your fuel mileage a lot. Other things to help that fuel mileage would be a tune up on your car, check the air pressure in the tires, how old is the air filter but as for that sensor(MPD) it stands for Manifold Differential Prssure sensor and I did try to find out where it might be on your car last night. But I shall look again today. But I mostly work on old cars say from 2000 and back. But that sensor MPD and those 02 sensors control lean/rich burn in the engine of your car. So you can see why getting those replaced would help your fuel mileage a lot. Whenever I buy a different car, I always do a tune up on it because you have no idea how the person before you treated the car. And again that would help your fuel mileage, check the air in the tires and get a new air filter. Also you should go to a parts store and buy a repair manual for your car. They cost around $20.00 and are well worth the money. It would walk you through where those sensors are and how to change them. But I shall try to another hunt as to where that sensor is at and will get back to you if I find that out. I do hope this helps you and God bless: