he is saying it is un-accelerating or slowing down. could need a tune up if it hasn't had one in a while other than that idk. is it a auto or a 4speed?
Sorry kiddo, that's not quite what he means when he says it's "Dieseling". Assuming the OP knows what dieseling is, it means when he shuts the ignition off the engine keeps running. Combustion without spark (like a diesel).
Does it do it for long? What kind of temps are you seeing on the gauge when it's warmed up? Have you put fresh gas in it yet?
More than likely the carb on that thing needs a good refreshing, if not replaced. I'd first try using some carb cleaner and see if that helps it out at all. It's a long shot, but I personally like to try the cheapest things first. 5 dollar can of gumout carb cleaner can't hurt. Lots of people just replace the stock carb with a Weber, but it's a bit pricey to do.