HELP! I'm at a loss

[damdog05]

within the last 2 months i have been getting miserably bad gas mileage. i only get about 150-160 miles per tank in the city, which is down from the around 250 i was getting when i bought the car last november. my problems started about the time i had my dpfe replaced in february. can something with the dpfe affect gas mileage that drastically? if not does anyone have any ideas about how to remedy this situation?

fuel filter and egr was replaced in november when i bought the car. oil was changed 1 month ago. spark plugs and wires replaced 2 weeks ago. stock intake replaced with a cold air intake and cone filter last friday. I have gone through 4-5 tanks of gas with this problem and have gotten gas from different gas stations i'm thinking its not bad gas. car idles fine, its smooth with no hesitation.

i have also recently cleaned the MAF, and run a fuel pressure test. with the car off and key on, i get around 20 psi, which is low. but at idle i get right on 30 psi and it holds there. my car didnt move at all over the weekend and i noticed a pretty significant drop in the amount of gas the guage shows i have, so im going to look for a leak tomorrow, and check my pcv valve. a tech at a ford dealership said check my cat converters but i havent noticed any decrease in power so i don't believe theyre clogged

I got 77 miles on half a tank last week so i need to fix this asap or i'll have to get rid of the car, and i dont want that to happen

I'll update when i get those things done but any input as to what might be my problem would be great!!! i'm slowly running out of options. thanks

 

[MustangLX-5.0]

Ok, DPFE is part of the EGR system. it's a Differential Pressure Feedback EGR circuit. And the DPFE varies the amount of exhaust gas that goes back into the engine, instead of relying solely on EGR vacuum. Too much EGR flow will stall the engine or cause it to run rough, because it will choke everything out with too much exhaust gasses. Too little exhaust gas flow won't cause the engine to burn more fuel. It just might set a code though. And speaking of codes, has your Check Engine light come on at all yet?

What year is this, and how many miles does it have on it? Fuel pressure while the engine is off is not important... unless you lose pressure by the second. Your pressure sounds alright. I would look into your O2 sensors. That is HORRIBLE mileage. Sounds like the engine computer is running in closed loop constantly because there may be an underlying problem. I would plug a code scanner into it and pull codes. Or head off someplace like Advanced Auto Parts and ask one of the employees there to connect a scanner to it and pull the codes. they will do that for free. You either have a bad MAF or a bad O2 sensor. Those are the 2 main things on a fuel injected engine that will cause fuel economy issues on an engine and/or cause major running issues. And I'm suspecting an O2 as you noted it idles fine.