To start off, I got the car about a month or two ago now and it’s a 2005 Mustang V6 with 137K miles, I did not know what the previous owner did so to start off, I got a new air filter, fuel filter, e3 spark plugs, spark plug wires and was running very good before I replaced those parts and ran even better with them installed, mpg went from 10.3 up to 17 or 18 so I was very happy... until today I went to go drive it and after 5 mins of driving, got into a turn lane and my car started to stutter and idle very roughly, my engine light has been on for a while since I had the car, and also I did get a new battery last night, it’s an optima red top Incase that’s related, but the idle is random, when I got the engine light checked, it said, EGR Valve, and possibly need to replace fuel sensor and I believe it said my fuel rail that something may be getting stuck, I’ll have to double check at the sheet to see what codes it gave but any ideas

 

I would say to start, clean the throttle body, and get you a new fuel filter. Easy stuff to do, and cheap enough to try. Maybe run some injector cleaner through it also. Then if it's still running rough move on the the other things. Hopefully some of the other members will chime in as they have more experience with the 05-09 S197's than me. Good luck.

And, welcome to the forum.

 

I installed a new fuel filter, when I’m driving I go to floor it and I feel and can’t hear my rear end a bit as if it’s about to fall out or collapse, it never had this problem, also when driving today was normal in the morning then parked, got back in it an hour or two later and I feel like the car was deaccelerating fast and accelerating, it felt sluggish like it couldn’t pull it’s own weight

 

You say the check engine light was On, so you need to post what ever engine codes are listed by a scanner.

 

Good deal, if you haven't yet, clean the throttle body. Mine would idle up to 2K then drop. Cleaning the throttle body along with the mass air flow sensor helped that. I don't know for sure, but the throttle body sensor could be a problem. And as Lime said, if you could post the codes you're getting. That could help us in helping you. Sorry, I'm not sure what the rear end noise would be.

 

Went to autozone since I lost the last report, here’s the codes:
- P0108 Barometric Sensor Circuit High Input
- P0193 Fuel Rail Pressure Sensor High Input

 

Hopefully someone can tell you what's needed my friend. I've never heard of a "Barometric Sensor", but then again there's a lot of sensors on cars these days. Good luck.

 

Those codes can be set if there is a vacuum leak somewhere. I'd be checking every vacuum hose I could find to see if they're disconnected, loose, cracked or collapsing.
I'm not familiar with the 3.8L V6 to help you hose locations. Usually there's an emission vacuum decal on the hood or rad cradle. After all that is checked you might want to do a search on how to check or clean the egr valve.

 

Your fuel pressure is whacky. The sensors work together to regulate fuel pressure. manifold pressure makes it fluctuate. If you can't get a solid pressure reading your fuel pressure will be off.

 

Thanks for all the helpful advice and tips, I finally stopped being a hypocrite and purchased a EGR Valve, and the fuel pressure sensor I bought last week... but still hasn’t shipped so I’m hoping it’s just because of the holidays but hoping to fix it soon before I go back to school soon, also off topic but I bought a little few mods I’m happy for and only paid $6 for, 3 Tire letter paint markers, black aluminum tire stem caps as the ones currently on the Stang from the previous owner is... green on a windveil blue car, I ordered LED’s for reverse lights, rear side markers, license plate lights, and all interior lights even the trunk light, also bought a Hoonigan key tag. All of these I can’t wait to put on even if they are just small things, the details add up but one question, when I go to replace the EGR Valve, it’s just a big nut and a few hoses correct? And when I replace the fuel pressure sensor on the fuel rail, will fuel squirt out or pressurized fuel will spill out the opening?

 

Green valve stem caps are used as an indicator to let one know when tires are inflated with nitrogen instead of air. Of coarse if you've bought the car used you won't know if the nitrogen is still in the tires or not.