Need a little help with a 4.0 EFI Explorer

[13 Z]

Guys,

I need a little help fixing my buddies Explorer. It has a 4.0L EFI in it.

It’s running really rough, to say the least. The moment I heard it run I could tell that is was missing.
When I hooked my scanner up to it I got 3 codes: P0304 (Cylinder 4 misfire) and two more indicating that banks 1 and 2 were both lean. I pulled the plug on #4 just to see what it looked like, and it was in great shape. All the vacuum lines are fine, and the MAF is clean as a whistle.

I’ve heard that the lower intake gasket is problematic in these engines, and that it might be allowing coolant into the engine. Other than that, I’m kinda stuck. I initially thought it was just the plug/wire, but that appears to be in great shape. Any ideas?

 

[blecoupe89]

Definately sounds like an intake/vaccum leak.

If this is a coil pack motor I would also change a couple around and see if the cylinder number changes.

 

[BuckChoklit]

Usually when there's a code that reads both banks are lean, it's a vacuum leak somewhere. I'd look for this leak first before trying to track down the misfire, because it could be related.

 

[greenstang1313]

not sure but is there any possibility it could be fuel related? Bad fuel pump, bad fuel filter, fuel injectors, etc... Just an idea.

 

[T-Bolt]

Is it the OHV or SOHC motor? www.explorerforum.com should help you out.