Just changed out my old cracked manifold and put in a new one..along with a new catalytic converter, muffler, and tailpipe. Start car and it sounds like a bad leak...no check engine light or codes thrown but smells like sulfur. Any ideas?...this is my third time changing a header on a xj but the last two were remix and had no problems

 

Soapy water in a spray bottle at the joints works pretty good for detecting leaks.

 

sulfur?
Wear garlic necklace and silver cross just in case.
2-3 wooden stakes wouldn't hurt...
1911 with silver bullets...

 

The sulfur smell is caused by raw fuel igniting in the cat, not good.

 

What would cause that???...car is all hooked up like it should be

 

The car ran perfect prior to the exhaust change...ugh

 

Anyone??

 

O2 sensor?

 

Since it's a new cat, the sulfur smell will be more pronounced as it's a lot cleaner and is oxidizing a lot more sulfur. Your older cat had clearly aged a bit, you wouldn't have noticed it much (or at all). The underlying problem is cheap gas with a high sulfur content. Try a different brand of gas and see how it smells in a hundred miles or so

 

Ah OK...gotta find as to why its running rough though

 

If it's running rough and it's loud, try out the soapy water tip that Bruce suggested. As for running rough, double check to make sure that new manifold is on there correctly, and triple check the O2 sensor.

 

Installed my intake gasket for a grueling second time and triple checked everything for flatness with a flat file. Made sure mating surface was clean and installed. Car hesitant at idle and runs like crap..header is brand new and o2 sensors are new also

 

If it is sounds like exhaust leak, find that leak and fix it!

 

Stock exhaust header or APN? It took two trys to get my APN right.

 

Stock style... with flex tube. The header is really nice and everything is flush against the head. Its driving me insane...can I try to loosen it and move it then re tighten the bolts??