I've got a 99 XLT with the 5.4. My question is this. At idle after the truck warms up, there is a strange noise coming from the engine bay. It sounds like a dull rhythmic thud. It's not all that loud but I cannot tell where it is coming from. I've opened up the hood but I cannot hear this noise outside of the cab. Overall the truck is running great. Even my idle is pretty smooth. I am averaging 18 mph. Could this be an exhaust noise???
Any suggestions would be greatly appreciated.