I have a 1999 7.3 diesel. I start it up when its cold to warm up. It goes on high idle , like it is supposed to, but the exhaust will hiss on and off not smooth and even . It also does it driving down the road it makes the truck jerk or lunge. If it is over 40 or 45 degrees it won't do it . Other than that it is a true work horse and will never own any thing else.

Where in the exhaust will this noise come from? Will it eventually stop?

Hi mark nat you hear it at the tail pipe when your outside the truck ,and you canhear it inside the truck (coming from the engine ) driving down the road.

It will stop sometimes and other times it won't

There is an exhaust flap actuator on the front bottom of turbo, this actuator will partly close the flap when cold to keep exhaust in engine to warm it up faster, when ecu sees throttle position the flap is supposed to open letting exhaust flow normal, this is a very common problem on 7.3s, you can either replace this actuator, or you can unplug it, if unplugged there will not be a check engine light and engine actually will still warm up pretty good.