Need help engine dies
Hey everyone im new to this site and very confused about how it works but i do need help i have a 1986 ranger 2.9l V6 but i installed a newer 2.9l V6 from a 1990 Bronco II. the issue is that it runs fine for awhile but at idle it will start to rev up and down slightly for awhile then dies but if i let it cool for a bit and fire it back up it runs fine until it happens again, it also bogs down getting up to speed in 1st and 2nd but seems to get going alright once i hit 3rd-5th none of these problems however happen until the truck is warmed up and drivin for at least 6 miles. the parts i've already replaced are the injectors and TPS thinking those were it but i guess not im thinking fuel pressure regulator, fuel pump??? if anyone could help it would be greatly appreciated!!!