? about fuel injection

Ok, since last september or so my car has been hesitating/stumbling when i am on it or i shift normally and get back on the gas at a low rpm. Its been so annoying i dont even want to drive the car. Ive changed the following things since then:

EGR valve/sensor
Fuel Pressure Regulator
Fuel Filter
Dist. cap and rotor
9mm wires
motorcraft spark plugs
Steeda thermostat/gasket
Optima battery
MSD ignition coil
Oxygen sensors
New Throttlebody gasket/IAC gasket/header gasket
K&N air filter

Also there are no exhaust leaks/vaccuum leaks/all wires are in correct order, timing is at 12*, It idles fine, and the coolant was completely flushed.

I dont know what else it could be, but im leaning toward the fuel pressure being messed up or the injectors being clogged or dirty. Ive been putting in Lucas Oil fuel injector cleaner since the problem started, and only put in 93 octane, sometimes 94 from sunoco. so basically my question is, has anyone else had a problem similar to this? Does anyone have any other ideas on what it may be? How hard is it to check fuel pressure, and if necessary to change the injectors? Its really frustrating that i cant figure this out, and i want to get her runnin in tip top shape before the weather breaks. Also, does anyone work for ford, i need to take the car in for a few recalls that the previous owner never did, the parking brake one and the elec. fan one, is it too late?? and how much will it run to get the codes read? i took it to Advanced Auto and they got no codes, but i think they did it wrong. Sorry for the long post, but i really need to get this fixed!!!

ECT: engine coolant temperature sensor
ACT:???

Also, the MAF is clean, as is the air filter and the IAT.

94greenvert said:

If you had an FPR I would say that you were running rich and should dial down the pressure. I had the same thing happen to my car and dialing down the pressure cleared it right up.

Click to expand...

Its not an adjustable one, just a stock replacement... all the parts i listed have been changed since the stumbling/hesitation started... things i thought could be the reason for it, but still havent changed anything. Also i had the battery out all winter while in storage, so the computer has had plenty of time to "reset".

TTT

Well, did some tests with the volt meter, the TPS, the IAC, and the MAF are all functioning properly... any other ideas guys? Thanks for the help too, you guys are great... if it werent for you guys and my dad id be driving it off the cliff!!!

TTT... hoping to get some more ideas before i take it to ford and drop 60 bucks to get the codes read

Well, went to the dealership... no codes, no charge but still no definitaive answer, they think maybe my plugs or wires are bad (even though they are less than a year old) Plugs are Motorcraft copper plugs, and the wires are FMS 9mm.... im gonna pull out all the plugs and re-gap them, make sure they arent damaged, as well as test the resistance on all the wires. Ill post my findings when im finished. If i need to i think ill buy the MSD wires and NKG plugs

Well, after spending probably 200 dollars on parts that i *thought* were the culprit, it turns out that when installing my headers i damaged one of my brand new sparkplugs... a $1.81 motorcraft copper plug, with a hairline crack in the ceramic, was the reason my car wouldnt run. So a word to the wise, even if its farily new, dont rule out a part that may be the cause of many many headaches. Thanks for all the help though guys, you kept me sane