Would a bad Cadillac converter make your van spit and sputter?

The ideal exhaust has no unburned gas in it. Since this hardly happens, a system to clean up air pollution was created. On the exhaust stroke of your engine, unburned fuel is forced out of your cylinder by the piston. That unburned fuel then makes it's way to the catalytic* converter. The catalytic converter basically gets hot to burn your unburned fuel and puts out the combustionally correct gasses.

It is possible that your catalytic converter is the reason your van is spit and sputtering, but there are also many other reasons this could occur such as:

timing

vacuum

fuel pressure

air

spark

Signs that it could be your catalytic converter include:

abnormally loud converter

abnormally shaky converter

hope this is somewhat helpful