I had the same thing!! cant say as you will be as lucky as me, but mine turned out to be a plastic walmart sack I picked up somewhere & it was melted to the catalitic converter.. I got as much off as I could & the rest took a few weeks to completely go away..
My cousin and i were driving in his tbird and i started to smell burning plastic BAD and his car was overheating well we got out and checked under the hood. The fan had started melting to the small case thing around it.