i just did a 4 banger ti 5.0 swap, now it wont run when in closed loop when warm, it will idle for about 20-30 seconds, then starts backfiring and dying out? i have even tried cleaning out the air bypass valve, have the idle turned all the way up, and have even tried disconnecting some of the main manifold vaccum lines, still wont stay running!! i have speed density, when i disconnect the MAP sensor, it will idle a little bit longer, but not much, please help!!!!!!!!!!!!!!!!!!!!!!!!! (i just did the swap, still have the 4banger fuel pump in the tank, wouldnt it at least idle and rev with the amaller pump?)
not necessarily, try unhookng the vaccume to the fuel pressure regulator which will up the fuel pressure. if ths helps it live a little longer that might hint at inadequate fuel. which your results after disconnecting the vaccume to the map sensor is hinting at to me.
what codes are you getting? im thinking that in closed loop, the fuel demands are less than open loop (which has higher idle and is richer).
can you goose it to keep it running, or does it die and not start again? have you checked fuel pressure and spark when it wont start (if the latter)?
good luck.