The Check Engine light is on in my 1998 4.6L F150 and my OBD2 diag tester tells me the code is for an "Evap Gros Leak". Any idea what this is? Pardon me, but I haven't really researched this yet. I was thinking maybe someone would know off the top of their head. The truck runs fine, there aren't any puddles under it, and no leaking gas smells! Dennis

 

I have the exact same truck (4x4) and had the same problem. Usually it is a gas cap (problem) not fitting tight. This system takes vapors from the gas tank and reburns them. That was not my problem. I had a hose that had come loose. Look real good because it took me (off and on) 8 months to find it. Otherwise, the only way to find the leak - is to use a system that injects smoke and look for the leak. This also can cause the engine to run lean and ping. Mine did and hasn't done it since I reconnected the hose. Good luck!