I have a 94 XJ 4.0 AW4 3"lift and 33s. I am only getting about 12mpg and I cannot figure out why.

Inside the TB is COVERED is soot, oil and gas. The whole CCV system is gunked up (just cleaned it all out a month or two ago). She idles smooth and runs great but she is dumping gas and I'm not sure why. I have a new IAC and TPS, many other new parts but those seem most relevant.

 

o2 sensors (first thing that should be changed when running rich), tune up (plugs, wires, cap, rotor), check for cracked exhaust manifold as well as other exhaust leaks

 

Shouldn't have any gas at the throttle body. Only air and crankcase fumes should go through it.

Maybe you should replace the CCV hoses?

Another thought. Pull the vacuum line off at the intake manifold. Make sure the fitting on the manifold is not carboned up.

 

Plugs, cap, rotor, wires, air filter and dizzy have all been replaced(replaced dizzy because the screws that hold on the cap snapped and I couldn't drill them out straight enough).

I am fairly certain my manifold is cracked but I have not verified that yet. and as far as replacing the ccv hoses can I use heater hose or does it have to be that brittle plastic crap?.

 

I'm more concerned about the small plastic lines being clogged.

Look at the vacuum fitting on the intake that I mentioned previously.

 

Which fitting specifically? I plan on pulling all of them today but I'm not sure if there is one I should be looking closer at.

 

I'm much more of a Renix guy, but there's gotta be a vacuum nipple on the intake manifold that supllies vacuum to the CCV system.