Hey it's been awhile since I've been on here for those who.don't remember I got a98 ext cab long bed 2500 5.9 magnum just dropped a fresh crate engine in about two months ago things have been running great since until now

I start the truck an it won't stay running unless my foot is in the gas now I'm thinking it is probably due to the pickup screen in the tank? What do.You guys think?

 

Moving to the correct section.

 

Was the iac swapped from the old motor? What condition is the battery in?

 

I figured out out I got to thinking an it did it before with the old motor an it was the tps I pulled it off an sure enough the o ring was bad let moisture inside.

Thanks for the help though. With the brand new motor I immediately thought fuel pump or the screen in the tank was clogged

 

Check your IAC Valve...I have a 99 1500 had this problem and fixed it right away.

 

I'd give the guy a break if he posted at the same time the OP was.

 

I've got a 1999 Laramie 5.9 that we were swapping out the plenum plate on when we realized the distributor cap was turned 180 degrees and wasn't locked down. After resetting the distributor and securing the intake manifold, we went to start it and the engine would surge to almost 2000 rpm's and then die. We checked the rotor position and made sure we were TDC and nothing changed. We replaced the IAC and that got us to the engine would still surge to around 1700 rpm's then flux between 500 and 1000 rpm's for less then a minute and then die. Nobody I've talked to has ever heard of this. I was hoping that someone here might have some ideas. I hope this is the right thread, kind of new at this.

 

Vacuum leak. Was the manifold properly torqued down?

 

Yeah, that was one of the first things we checked. Also, sprayed carb cleaner around the seam to see if one of the gaskets shifted. Nothing there either.

 

Mine was doing that. Turned out to be a dead cell in the battery.

This was to the OP. Sorry. Seems this thread is older than I thought.