Three times in the last two weeks I've been traveling down the freeway at about 65 and my Geo Metro has sputtered and a puff of white smoke has come out ( I presume ) the exhaust: I can see the "puff," which is fairly substantial, in my rear-view mirror. The car seems to run fine after this happens, but it is scary as you-know-what. Any suggestions as to what might be happening?
Thank you, people.