03 mustang gt sputter/miss

hey guys, i have been trying to fix this problem for god knows how long and no mechanic near me can help, believe me i have tried. I have sompletely lost faith in mechanic in my area, So im left on my own to fix this.

My car has been sputtering for around a year now and i cannot for the life of me figure out why. I have replaced the fuel pump twice, the second time was for a larger pump bc i have a procharger waiting in the garage to be installed. I have changed the fuel filter and the plugs (ngk platinum). Ran o2 sensor deletes to the rear o2's bc i threw a bbk offroad H pipe on. I even replaced the upstream o2's. And still i have a horrible sputter through each gear. And to top it all of my car has recently started cutting off on me while the rpms are low. The idle will start jumping a little bit then drop completely and the car will cut off, especially when im running the lights and heater. So went to advanced auto to check my alternator and bettery, both are perfect????????!!!!!!

My mods are accufab 75mm tb & plenum w/ steeda spacer, jlt ram air intake, hypertek thermostat, steeda underdrive pulleys, mac long tubes, bbk offroad h, mac catback, 410 gears, steeda tri ax shifter

PLEASE HELP ME

i'd say it has something some problems coil pack or ecm or called a/module/.

o forgot to mention it has an sct flip chip w/ a dial & 4 tunes .... would there be any way to tell if a coil pack was bad by looking at one ?? Or is that something i would have to get a mechanic to check out?

Just looked over my engine and i notive something that i had cleaned up before and forgotten about. My driver side valve cover has the breather hole in it (im guessing thats what it is) and the hose connected to it runs to my intake tube. Well where my valve cover connects to that hose there is what looks like oil splatter on my cover? Im pretty sure that isnt supposed to be there?

Check the PCV to see if it is working correctly. It should rattle when shaken and you should be able to blow into it one way and not the other way. Check all of the hoses for a vacuum leak.

My 1991 GT was having the same problem. Like, the lights and running the heater would cause the engine idle to go really low. And sometimes I would have to rev up the motor (sputtering and misfiring) till finally it would finally idle at a decent RPM. It especially ran like crap in the winter when I would run the heater, fog lights, windshield wipers...etc...etc. Any how, at the time, my alternator was less than 3 months old, I had it tested at two different Autozone stores. And well, both times the alternator was good. I checked my guage cluster...I checked as many relays as I could find...I disconnected and reconnected damn near all the electrical connectors as I could find....I was scratching my head and feeling like an idiot because I couldnt figure out what was wrong with the mustang. So, I finally gave up and parked my car till last summer, by the way, It's a convertible. Any how, I pulled the car out of the garage for a little summertime cruising...with the top down ofcourse!!!!!!! The air conditioning system wasn't working, so later that evening I pulled the A/C knobs out to inspect the connector...it was loose...I plugged it back on tight and the A/C system was good again........I take the car out for a drive with the A/C blowing ice cold and all of a sudden, the battery light comes on in the dash cluster....and then the car dies out completely. It seems that the air conditioning was more than the weakened fusible links could handle. I trailer the car back home figureing the alternator finally went bad...I had it checked out AGAIN!!! and it was good...now I'm thinking WTF...as it turned out, THE FUSIBLE LINKS WERE BAD causing the GOOD alternator to NOT send enough current to the solenoid. The alternator was sending enough current to barely charge the battery, but not enough to run the cars systems....SOOOOOOOOOOOO...what I did on my car to fix the problem was this: I cut the two fat wires coming out of the alternator...I think they were black with a white stripe...I took each of these two wires and connected a fairly thick guage wire onto each one...I then ran the 2 strands of wire around the front of the radiator and over to the area near the brake booster...I then took the ends of those two wires and connected each end to a fusible link that I got from a 1990 Honda CRX. The fusible link has the ability to pass power thru 3 links. And the power ratings of the Honda fuses are 55 amps, 45 amps and 45 amps. For a total of 145 amps. I am only using the two fuse links rated at 45 amps for a total of 90....My alternator is only able to put out 75 amps so I think it will be fine. So far I haven't had any problems....No eratic idle...no mysteriously dead battery....Anyhow, the reason I used the Honda pieces is because the Ford wiring system was difficult to remove and replace. Any how the honda links and the rewiring took about 45 minutes to complete. I think it took more time trying to locate a suitable and simple link system. If you want to try this out on your own, you can find the Honda fusible link bolted onto the passenger side strut tower.