Ok. My car misses a little bit at idle. I took out the AIR system and crimped the metal pipes sticking out of the exhaust manifold. Once I got them all sealed up so no exhaust could escape, my car ran really bad. It would die at every stop sign and start shaking at idle and then die at idle. Then I uncrimped one of the pipes.....it ran like normal. When I covered up the pipe.....the engine started shaking again. Also when it misses, gray smoke comes out of the exhaust....does this mean it is too lean? too rich?

 

something is plugged in the exhaust. either the cat, crushed pipe, or the muffler.

 

How could such a little tiny exhaust leak like that cause the car to run soo much better? It runs almost like new with the leak, but with the pipe crimped I can't keep it running. I'm going to clean out my catalytic converter today if I can only get the rusted exhaust clamps off. It sounds ***** and high pitched with the little hole in the exhaust manifold.