Hey guys, first time poster here but I am at a loss with my truck and looking for a little guidance or help. My truck is a 98 f150 v8 5.4 with 137k original miles. I've had some issues lately...

First I had a vacuum leak on my pcv lines..3 of the rubber elbows were blown out. Well a couple days afterwards I started hearing hissing again so I checked the lines for a vacuum leak again but no luck. That was roughly a week ago. Well yesterday I went to leave and went to start my truck. It turned over, started up but then revved itself up to over 3k rpm. It then went way down to about 400 rpm and sputtered out and died. I can still start it but get the same result and still hear it sucking air really bad from somewhere (I can hear it in the can because of how loud it is.) Any suggestions on where I need to check and what I can do? Not the smartest on vehicles but can get by with guidance. Thank you!

 

Sounds to me like your intake tube is disconnected from the throttle body.

 

Will check it.