Starting problem
 

Ok..if I take the Mustang out for a little while...mostly on just short runs here and there....when I go to start it again it won't start...I have to put the pedal to the floor and crank it until it does..basically, treat it like a carbed car. BUT it's EFI!! What is up with that? Leaky injector or something? SEEMS like it's flooding.... Thanks everyone.

starting problem
 

process of elimination. start by giving it a full tuneup-
replace cap, rotor, plugs [.54 ] wires, fuel filter,air filter, pcv.
if your stang has over 80k on it i would definately recommend replacing the o2 sensors & the tfi module . the o2 sensors can cause drivability problems & the tfi module will cause a car not to start again if already warm-just as you described. i recommend all parts said, to be replaced for a much healthier running pony.

Are the O2 sensors located on the headers or the downpipes? Don't recall seeing them but then again I haven't examined the car THAT throughly. It's dark and cold out and I'm recovering from a 102.5 fever, so..no outside for me right now!! And....what is the TFI module? I recognize everything else but I've never heard of that one...

The O2 sensors are on the h-pipe by the cats. There is one on each side. The TFI module is on the distributor shaft. It plugs in to the harness.
Caymon

Well thing is..I have an X pipe, with no cats... Don't see any O2 sensors anywhere...no check engine lights either though. And what does the TFI module do exactly?

They should be between the header and where the pipe makes the turn towards the rear. They should screw into the pipe and have a connector plugged to them.
Caymon

I'll look again but I didnt see anything. None of the pipe is original..it's all been replaced... Didn't see any sensors in there but I'll have to double check. For me not to throw a Check Engine light without O2 sensors, the light must either not work or the ECm (is that what you call it in fords?) was tweaked with to work without O2 sensors.

That is strange. Replacement pipes should have holes for them. My off road x-pipe does and every other one I have seen does as well. The o2 sensors are pretty inportant and I know that 91's have them. If I'm not mistaken, they assist the computer in adjusting your air/fuel ratio and I can't remember what else they do. Your computer should throw a code without the sensors.

Caymon

Yeah. I'll double check in the morning. I've dealt with O2 sensors before, I know exactly what they do. O2 sensors don't work in a cold engine, so the computer runs open-loop until a few conditions happen...one is a certain operating temperature is reached, and another is the O2 sensors put out a steady reading. They dont read within the proper voltage when it's cold so the computer ignores them. Once they warm up, it uses a combination of MAF data, MAP (if these cars have these as well..I know older MAF Camaros had MAP's as well they just werent nearly as important), throttle position, and O2, among others, to calculate a proper A/F ratio once closed loop is achieved. Without O2 sensors, car would..hmm..PROBABLY run rich, since the computer would set a default which is probably the default it uses in open-loop operation.