I need your help! 4.0 Misfiring!!

[adsm08]

I would also suspect timing chains if the concern was consistent across the temp range. He said it's fine once it warms up. The O2 code is not part of your driveability issue, it's just for the heater.

The fact that all of bank one is involved and there is a code that seems to relate to fuel pressure makes me suspicious of the fuel system. The 4.0 uses a returnless system, and the fuel comes into the rail on the bank 2 side, meaning bank 1 gets fed last. Low fuel pressure will have a disproportionate effect on bank 1. I would do a fuel pressure test to start.

You can also swap all your plug wires side to side at the coil and recheck for the misfire codes in a day or two, see if they changed cylinders. That would point to an issue in the coil pack.

 

[jsavage977]

Alright now. Thanks everyone for all of the input! I went to Vegas over the three day weekend and I decided to take it to a shop and let them tinker with it for a few days. They let me know that it has a crack in the intake manifold. They claim that they found the leak using ether and they are pretty confident that is the problem. They are good friends and they offered to give me their price on all the parts and help me out with labor which is good. I could do it myself and have parts strewen across my driveway for a whole evening likely two or three hours and pay full price for the part and gaskets, or I can pick it up tomorrow and pay about $300 and drive it home. I am leaning to having them do it for me tomorrow.
So my questions for anyone who might have seen this before:
Are these plastic manifolds prone to cracks and leaking?
Is it more likely a intake gasket problem?
And am I underestimating this job and it will only take me 30 minutes with my handy impact driver?
Again thanks so much for your help.