trivia
Laughing Gas
Joined: Jul 2001
Posts: 1,019
Likes: 3
From: Bismarck, ND
trivia
I'm not an expert on the 4.0L, but applying basic EFI theory to it...... one thought that comes to mind could be a faulty fuel pressure regulator. These are designed to keep incoming fuel pressure at a constant and lower pressure. As fuel leaves the pump at a high volume (and pressure), the regulator steps it down to a manageable amount. From there, it is fed into the fuel rails and injectors. If the regulator fails, too much fuel can enter the rails, injectors, and cylinders. Too much fuel entering the cylinders will result in excess finding its way into the crankcase, as it will not be completely or properly burned in the combustion process. I would think that this would also result in your truck running rich, though the high-energy ignition systems in today's engines can burn richer mixtures before fouling spark plugs (I would still think your O2 sensor would smell a rat, though). Are you getting any kind of error codes or "check engine" lights?
