I have been trying to track down a running rich problem and noticed that I have major oil blow by causing my throttle body having oil residue in it. Could this cause black/ blue exhaust? I know I have a exhaust manifold leak...

I bought 2 crankcase breathers and some vacuum caps. I think I'm going to breather the first vent (closest to the front) then figure something else for the pcv....
Any ideas?

 

Black buildup in the intake and throttle is normal due to crank case fume scavenging.

The Jeep 4.0L does not have a PCV valve. It's called a CCV system and airflow is constant. The forward assembly is just an open tube that draws fresh filtered air into the valve cover. The rear assembly had a different elbow "metered orifice" that goes straight into the intake manifold. No valving. This is how oil winds up in the intake. Both front and rear lines and elbows should be cleaned/replaced.

Blue smoke is normally oil. Black is fuel from running rich.

I'm assuming your XJ is a '94 from your username? (Please always post this!) Check that the vacuum tube from the throttle body to the MAP senson on the firewall is clean, connected, and not broken.

 

94 HO 265,000. breather tube for map is clean and replaced, 25,000 ago. There is not black build up but juicy brown oil.

I am aware of black residue by not this fresh oil...

Im going to put a breather on the front elbow to hopefully keep the oil from going into the throttle body. Back elbow I will probably keep in stock locations.

 

Ah so a lot of fresh oil. That's not that normal.

Front elbow has nothing to do with oil getting into the throttle body... that's how air gets in. Are you getting oil on your air filter?

First thing to do is freshen the CCV system with stock parts. Leave the modifications alone until you figure out what the problem is.

"Replaced 25,000 miles ago" is a looong time my friend. It needs to be inspected. Broken/disconnect MAP tube is the #1 cause of really rough running on older XJs (1997+ doesn't have that tube)

 

Thanks for the reply!

Yes fresh oil.... I have an afe stage 2 which isn't affected by the oil blowing by. The vacuum line is good. No weather cracks and a tight fit on both sides. I cleaned also. The only bad vacuum elbow I have is the one that hooks the fuel pressure regulator to the intake manifold. Which I cannot find the vacuum line! So I siliconed it in the mean time.

All of the other lines are good. No stress cracks but will be cleaning them today...