1997 explorer sport doesnt run right

[ywingplt2]

i have a 1996 ohv 4.0l straight drive explorer,with 255k miles on it , let me just state when it wants to run it runs like a brand new one. my check engine light is on the code say right bank 2 lean and large air leak, i have replaced all 3 o2 sensors along with wires and plugs, i done the carb cleaner sray test to find the air leak but no luck on that, my biggest problem is after it sits for awhile it will crank and cut off a couple times then run fine , once i drive to work or home is the problem after a long drive and i shut it off it doesnt want to crank motor turns and when it does fire it struggles to run i can pat the gas but it doesnt do anything for at this point i will hear it kinda sound like its back firing , and like the motor just developed a bad az knock. all this takes about 10 minutes b4 it will run right so i can drive it at which point it runs like brand new. any help would be great

 

[SoHK_alumni]

1st guess is intake manifold gaskets, a common issue with the 4.0.

 

[Sedition]

Vacuum misfire ~ Intake manifold gaskets. When its cold they aren't sealing properly. Once it's warm they seal again.

 

[Turdle]

Agreed, also don;t forget to install new o rings on the injectors.

You might check the PCV hose, look for an open port on the vacuum tree to the rear driver side of the upper intake manifold. Some have a cap on one of the ports which may fly off.