Think i found why I've been running so rich....

 

good find, You going to replace it or weld it?

 

if your going to replace it spend a lil bit more and get a true header

 

x2

 

a cracked header doesnt make a engine run rich.

 

if it is before the o2 sensor it does, the o2 sensor will sense too much air in the exhaust, creating a "lean" reading to the computer, the computer then compensates by adding more fuel.

 

i dont think that crack would affect the flow to the o2 sensor that much idk though

 

i had the same problem back on my 88, crack in the same spot, fail smog due to a 13-14% O2 reading, it is supposed to be .5%. so it definitely has an effect on the O2 sensors and fuel ratio

 

wow i didnt think jeeps were that smart haha. well my header cracked in the same spot a couple weekends ago heading up to naches. so ill keep that in mind, i dont care if my jeep runs rich, rather have it run rich than lean any day.

 

A crack in an exhaust manifold will leak exhaust because the pressure is higher inside the manifold than outside. You won't get too much air. When a car runs rich, you know it.

 

you also loose back pressure. Get it fixed