Engine problems with my 95 5.0 mustang?

Question

I have a modded 95 5.0 mustang and lately its been having issues. The check engine light is on but whoever owned the car before me must have cut wires or something cause no computer will read it and throw a code as to whats wrong with it. When its running the idle with go up and down constintally the rpms go so low sometimes that it almost dies and sometimes it does. I've tried replacing the msd coil and put all new msd plugs,wires,cap rotor and runs the same no shop seems to figure out what the h***s the problem idk why. It goes through premium gas like crazy, all the sensors were checked and cleaned i need it to run right. i always have to rev the c**p out of it in first gear or it will die. also i have a cobra r hood with 2 holes and when i get it washed it runs like c**p after i get out of the carwash. PLEASE HELP ME IM DESPERATE!! THANK YOU SOOO MUCH FOR ANY HELP i just dont want to spend a million dollars on parts if i dont need them i've already had to take parts back to napa cause it didnt do anything car still ran the same some of the mods i have r 373 gears,nos,long tube headers,underdrive pulley kit, msd ignition (just replaced 7 months ago and is in the car) msd coil (just replaced 6 days ago)

Answer 1

oh problems with ford again if you had a chevy there will be no problems

Answer 2

If you have an aftermarket PCM or chip installed then that is your problem neither one will not communicate with a scan tool.  

Answer 3

you need a biger shot of nos, naw just kiddn. the reason the idle gose up and down is cause of the idle air control valve (IAC) try that or a vacume leak some where mabey behind the ac controls or something on the intake, also the reason it runs ruff after the carwash is cause the distributor gets wet take some wd-40 and spray it when it happens.

Answer 4

first off you need to get the wiring sorted out for the OBD so you can scan it check and make sure theres no corrosion on the terminals I have had issues with this on the under hood ones B4

you may not be able to solve anything till you can scan it get you the wiring diagram and run the wires right off th ECM iff needed you only need 3 as I recall to scan it. and just for the record its never a good idea to buy the modded stangs unless you know what you are getting into. AS a last resort you can always convert to carb some guys prefer this anyways (not me ) but others do being a 5.0 its not that tough to do otherwise check out the stang sites they may be able to offer more help