88 Bronco runs bad after warming up

[centex]

Hi all. This is my first post to this list. I work on a lot of other cars (mostly foreign) but I'm having some trouble with my pony. Completely stock, 1988 bronco, 302 with 160000 miles. It starts and runs fine for two or three minutes but then starts to run rough. When I start it there seems to be and exhaust noise on the passenger side; as if there was a cracked manifold. When it warms, the noise lessens. I ran some better gas through it with some cleaning agents but that did not help. I'm not sure where to start with this one. Thanks in advance. Centex Jim

 

[Seabronc]

You probably have diagnosed it. A cracked manifold will do just what you described.

Good luck,

>-

 

[Blue beast]

Pull the codes on it either with a reader or with the paper clip or meter method. And tell us what you get. If it's a cracked manifold you should see evidence of exhaust geeting through black spot or something look for the gasket area too!!