if its a misfire, you could just need to get new plugs or one of the coil packs may have gone bad. you really could stop by autozone and have them check what code is being stored for free before going to the dealer to verify the problem is ignition related. you can post up the results from get the codes scanned and we can try and help you from there. otherwise, take it to an isuzu dealer and have them work on the truck.