Rebuilt engine in 96 mustang,engine is stalling and sometimes dying.Put on machine and it said 2 and 3 are misfiring.Found out today someone replaced one of two oxygen censors with one that was for a tauras but had to grind it down to fit would this cause these problems

this 17 years old a good run. nothing new here on failures this old.
all car fail that is what they all do eventually. (entropy etc)
let me guess never fails in others hands
and scans show nothing wrong, but sure too late then, they are gone.
so is and engine problem, so we focus there.
engines (gas, in order fail for 3 ways)

1. engine is bad, or cat melted (no) and egr stuck open (no)
2. bad spark (fuel can not burn lacking spark so why skip #2?)
3. bad fueling. too much or too little

in that order,

not enough evidence stated.
RPM's sink on start sometimes dies then usually it catches itself, idles high a few seconds then lines out.

runs great hot engine, so I guess fails only cold engine.
so bad spark plugs, bad spark coil boots or bad COPS
or bad CKP or CMP
why not just put in new plugs and new boots,
17years old those are NEVER GOOD.

ENGINE IS: 3.0L 2v or 4v (means 6x2 =12valvs or 6x4=24vavle heads.???? it has COPS, coil over plugs(spark)
6 cops ,6 new spark plugs and 6 new boots.
or learn now scan and drive,
or scan in the morning dead cold as the RPM go nuts
and does it misfire going nuts the RPM> misfire is spark first
or flooding 2nd the cold fast idle speed is wrong (IAC)

all I here is almost STALLS at cold start means why below 800 rpm hot and 1500 rpm cold so stalling is what MISFIRE?
can you prevent the too low RPM and stall with fast right foot action?
I say bad spark if not bad spark that is leaking injector or pair

learn to listen and feel for misfire,
and to use the right foot , adding throttle extra air to make it burn clean. Misfire s mostly violent. felt , heard, and see if you view the engine shack.
that is all I have but scanning it failing is how you fix cars

nobody can fix working car delivered a work car...
I have scan tool that logs and then play them back and bingo
GOTCHA. (P0306, and number 6 injectors is bad) see?

replace fuel filter and if it continues have pump pressure checked

check for a fuel flow problem( pump pressure-filter blockage-injector/s) run fault codes ( check for HO2S and O2S sensor operation.. Check cat converter is serviceable Blocking exhaust system

try testing/replacing the coil. if it stalles after the car warms up that gives the coild time to over heat and die.

check fuel pressure -fuel filter/fuel pump--also check for vacuum leak or hose disconnected

bad plugs and wires replace wires once a year

Start with the simple and replace the fuel filter. The fuel filter should be replaced every 15,000 miles or once a year to ensure the fuel system is running 100%. Auto Zone will have the fuel filter and can give you the step by step instructions to getting the job done with common tools. If it's the fuel pump failure, you have not gotten the car restarted. Good luck and keep me posted, be glad to know you got your car running 100% again soon and please rate.

FORD: 1995-96 CONTOUR, CROWN VICTORIA, ESCORT, TAURUS, THUNDERBIRD
1996 MUSTANG LINCOLN-MERCURY: 1995-96 CONTINENTAL, COUGAR, GRAND MARQUIS, MARK VIII, MYSTIQUE, SABLE, TOWN CAR, TRACER LIGHT TRUCK: 1995-96 AEROSTAR, BRONCO, ECONOLINE, F-150-350 SERIES, RANGER, WINDSTAR
1996 EXPLORER This TSB article is being republished in its entirety to include the 1995 4.6L Thunderbird/Cougar. ISSUE: After a 1-4 hour engine soak time, long crank times and/or long crank to start followed by a stall may occur on some vehicles. No further stalling or rough idle will occur after the engine is running. The long crank and/or stall may be due to the Idle Air Control (IAC) Valve sticking.
ACTION: Replace the IAC Valve with a revised IAC Valve if no Diagnostic Trouble Codes (DTCs) are present. Refer to the following Service Procedure for details.
SERVICE PROCEDURE

1. Perform normal diagnostics and correct any DTCs as required by referring to the appropriate year Powertrain Control/Emissions Diagnosis (PC/ED) Service Manual.
2. If no codes are present, replace the IAC Valve by referring to the appropriate model/year Service Manual, Section 03-14. Refer to the following Idle Air Control Valve Application Chart for proper IAC usage.
   
   IDLE AIR CONTROL VALVE APPLICATION CHART Model Year Vehicle Engine Revised Part Number PASSENGER CARS 1995 Escort/Tracer 1.9L F5DZ-9F715-BA 1996 Escort/Tracer 1.9L F6CZ-9F715-BB 1995 Contour/Mystique 2.5L F5RZ-9F715-AB 1996 Contour/Mystique 2.5L F6RZ-9F715-AA 1996 Taurus/Sable 3.0L 4-Valve F5DZ-9F715-DA 1995 Taurus/Sable 3.0L 2-Valve F5DZ-9F715-EA 1996 Taurus/Sable 3.0L 2-Valve F6DZ-9F715-DA 1995 Taurus SHO 3.2L F6DZ-9F715-CA 1996 Taurus SHO 3.4L F6LZ-9F715-AC 1995 Taurus/Sable 3.8L F68Z-9F715-EA 1995 Crown Victoria/Grand Marquis/Town Car 4.6L 2-Valve F5PZ-9F715-AA 1996 Crown Victoria/Grand Marquis/Town Car/Mustang 4.6L 2-Valve F6AZ-9F715-EB 1996 Mustang 4.6L 4-Valve F65Z-9F715-BC 1995-96 Continental 4.6L 4-Valve F5OZ-9F715-AB 1995 Mark VIII 4.6L 4-Valve F3LZ-9F715-AA 1996 Mark VIII 4.6L 4-Valve F6LZ-9F715-AC 1995 Thunderbird/Cougar 4.6L 2-Valve F5PZ-9F715-AA 1996 Thunderbird/Cougar 4.6L 2-Valve F6AZ-9F715-EB LIGHT TRUCKS 1995-96 Ranger 2.3L F5OZ-9F715-AB 1995-96 Ranger 3.0L F67Z-9F715-AA 1995 Aerostar 3.0L F68Z-9F715-DA 1996 Aerostar 3.0L F69Z-9F715-AA 1995-96 Windstar 3.0L F68Z-9F715-DA 1995 Windstar 3.8L F68Z-9F715-EA 1996 Windstar 3.8L F68Z-9F715-CB 1995-96 Econoline/F-150-350 Series/Bronco 4.9L F68Z-9F715-EA 1996 Explorer 5.0L F67Z-9F715-BA

it sounds like either the torque converter solenoid is stuck or the torque converter itself is bad

im going to just throw this out there but it could be the stand pipe in the fuel tank.i have a 96 gt and when i come to a hard stop or right hand turn the engine will turn off complety and sometimes will start back up so any way the only way to check this prob is to drain and drop down the fuel tank and see if there is a problem in the tank good luck