This past Tuesday I finished replacing the lifters(new lifters, rocker arms, pushrods, valve stem seals, etc) & on my truck. In the process of putting it back together I cut one of the orings for a fuel injector. It ran ok for a day or so bt then the pressure caused it to fail. It started spraying gas everywhere(several gallons worth in maybe a minute or so).
After replacing all the orings on the fuel injectors the truck ran great. Friday on my way home I went from crusing at 45 to 25 very quickly. the check engine light came on at the same time.
I stoped and opened the hood. The engine sounded normal. As I walked along the passanger side it sounded like there was a potato(e) in the exhaust.
I limped home the last few miles.
Saturday I was turning the truck around to take a look at it properly. Everything was fine. Ran up and down the street a few miles with no problems. So I got braver. Made it about 5 minutes before the same thing happened again.
I am thinking that after 13 years and 220k miles the converter has given up the ghost. Once it gets hot it clogs up (possibly also caused from a lot of fuel dumping into the engine from the failed oring?)
Before I just go and buy a new converter & exhaust system(a cat back sytem was my much needed next project for this anyway) I wanted to check and see if it is the converter. (I have never had one go bed beforeso I dont really know the symtoms)
Check your code first. The PCM wants to tell you something.
A bad cat can do what you describe. The honeycombs on the inside physically break into chunks and when they turn sideways, gases don't go through them to well. My old VW Jetta did this and it bucked like a bronco for about 20 seconds, slowed down to a crawl, I put it in nuetral and blew out the motor, then it was fine. Good thing too as I was in the middle of a 3 mi long bridge with no emergency parking lane.
But there are other things that can do this, conceivably a MAF meter, IAC valve, bad coil - who knows? Go to this web page for a list of codes. If it is the cat, a O2 code might occur since you sensor is just upstream of the cat.