I changed both upper and lower intake gaskets along with the engine coolant temp. sensor, and idles like brand new. My upper gaskets were fine but the lowers were leaking between the ports. I bet if you put lower intake gaskets on it will fix the problem.
Thanks CRD...
I think this is going to be where our problem was. Once I was able to inspect the gaskets, I thought to myself... Woah, this has got to be it. The gaskets were so stiff, it almost felt like they were brittle as I was removing them.
I just finished the job, and proceded to move the rig out of the garage to let it "cool off" for a few hours. I'm hoping that sitting outside for a while will simulate a cold start. (I should hope it does, it's a balmy 17 degrees here today) They're forcasting a low of +4 tonight, so I guess in the morning, is when the real test will come.
Here's a couple photos of what it looked like when I pulled the lower intake off... I'm guessing the mouse nest is optional. LOL
Just for reference, this vehicle is a
2000 with the 4.0 SOHC in it.
Note, in the photo below, the brownish/greyish rings... those are the gaskets. See how the inside (towards the middle of the manifold) and the outside (towards the edge of the manifold) of each gasket looks different? This must be where the engine was sucking air.
Here's the lower, with the new gaskets installed.
I'm pretty confident that I've found the problem. Again, thanks to everyone that weighed in on this topic.
Mike De