[kwhauck]

Car is a 2000 Grand Am with a 2.4 4 banger. So a couple weekends ago I swapped the new motor in. The old motor was knocking so hard I didn't bother paying attention to any other problems. Finally having time yesterday I finished everything up and fired her up. Started no problem, but stumbles hard intermitently. After a couple minutes I threw a P0300, multiple misfire. I also am getting a little smoke from where the exhaust pipe meets the manifold. I did spray some pb blaster on the exhaust manifold to get the nuts off so maybe it was burning a little. I am thinking clogged cat though? Any other thoughts. This is the first time I have worked on these 4 bangers.

Thanks, Kyle