Prayer for a Mustang God

Backfiring out the intake is a sign of an excessively lean mixture. The car starts in open loop and is OK. When it warms up enough to go to closed loop, then you have problems. Look for things that start to operate only when the engine goes into closed loop mode.

Backfiring is either a valve stuck open or a lean mixture or spark plug wire(s) connected to the wrong cylinder(s). Check compression on all cylinders and then look for vacuum hoses loose, cracked, misconnected. Check the line for the vapor recirculation system – it is easy to knock loose and not see it when you connect the air pump plumbing. If the vacuum line for the EGR valve and the air pump are cross connected, some very strange things can happen. Check the mass air flow electrical connection and see that it is tight, the same goes for the fuel injection wiring harness connectors up on top of the manifold near the firewall.

Lean fuel mixture breaks out into several sub categories:
A.). Vacuum leaks
B.) Air entering the intake without passing through the MAF
C.) Failure of the MAF, BAP/MAP (Baro or Manifold Air Pressure, same sensor, different name), ACT (air charge temp), or ECT (engine coolant temp). These should set a code in the computer.
D.) Leaking exhaust gases from EGR valve at WOT.
E.) Clogged fuel injectors.
F.)Fuel injector wiring problems causing injector not to deliver rated flow.
G.) Computer problems: (computer problems are not common like sensor problems)
H.). ROM has bad data in fuel or timing table. This should also set a code in the computer.
I.) Failure of one or more of the computer's driver transistors for the fuel injectors. No code set on this one.
J.) EGR not opening at cruse power. The computer adds timing advance to compensate for the slower burning speed of the EGR diluted intake charge.
K.) MAF calibration off or mismatched to injectors.

one of your codes is the evr failure, which controls the egr valve, if that was going bad, could it engage/disengage the egr valve at the wrong times possibly? more of a question

Also check the IAC

Your car is run by demons of hellspawn

call a priest

damystikal69 said:

This is what I have changed so far. Fuel pressure regulator, Fuel injectors, fuel pump, fuel filter, IAC, coil, checked all vacuume lines, cleaned the MAF, adjusted the TPS, played with the timing, checked plug wires, changed plugs, and it still runs the same. If the car runs for about 5-10 minutes it wont backfire or load up. Even if I drive for an hour I still have to let it run for 5-10 minutes before I take off. If I start it then take off it will drive fine for the first 5 minutes then it starts missing, backfiring, running like crap. This all happens for about 5 minutes. Then it seems like it cleans its self out and you can feel it clear out. After it clears out it will run fine all day long as long as the car stays running. once you shut it off then it starts over again. Thats even if you shut it off for a second. I have alot of time and money in this car and would love to have it running right. any suggestions is greatly appreciated.

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Use a vacuume pump and connect it to the EGR and see if it will hold a reading.

Have you eliminated the MAF sensor as the trouble , by changing it for another one yet ? Had a bad MAF sensor on my mustang(Shock damaged by a fender bender) and had all kinds of wierd drivability problems after, was very hard to find.
Thing is a BAD MAF can just put out the wrong numbers, but still be within a range of values that won't cause a code.
Hope this is usefull info.
Sincerely,
Hink