CEL came on over the weekend and is reading out that the motor is running lean. We put a fuel pressure gauge on it and it's at 31psi at idle... I've searched and searched and haven't found a definitive answer as to where a 2000 4.0 sport should be at fuel pressure wise at idle.

Before the light came on it was running fine, but had a severe issue with restarting when the motor was hot. I thought it had to do with the fuel injector heat sink problem, but now am not so sure after the code was for it running lean. I also don't think it's the heat sink issue since I pulled off a vacuum line from the manifold, plugged it up, and had no issues restarting it when hot. That vac line was coming from the charcoal canister purge valve.

My buddy suggested I change the fuel sending unit and filter since I'm at 160k and it hasn't been changed my knowledge. Anywhere else I should look that would cause these issues?

 

Changing the sending unit will get you approximately nowhere, however the filter may. I believe the 2000 models are supposed to be around 40 psi, +/- 5

 

Aren't they one piece? Or is it one of those "might as well since you're in there" situations...

I'm guessing the fuel filter will help out. Perhaps the fuel pressure regulator as well? It runs a hell of a lot better with the one vac line unhooked and capped at the manifold from the evap purge valve. Perhaps that should be replaced as well...