Hey guys. My lightning has 50k miles on it and a couple days ago it started acting a little funny. It does it when it wants to aparently but sometimes when i start it up, the rpm needle gets stuck right above 1k on it's descent and makes a womp womp womp sound. Also the noise occurs sometime when i amp driving after it's reved up a past about 2k rpm and sometimes when i put the truck in reverse. I discovered that the sound was coming from the intake and only got louder when i disconnected the air box. I ordered a new instake because I also discoved the filter was horrible. Anyone happen to know what causes this sound or have experienced this before??? Thanks

 

Sounds like your idle air speed motor on side of plenum is bad.

 

it idles fine

 

Disconnect the IAC cable when its making the noise, If it's that the noise will stop. If you need a new one get it from Ford and not from aftermarket supplier.

 

i disconnected all of the plugs on the intake and the noise kept comin. i have a k&n intake on the way, and i'm gonna have a mechanic look at it. i'm stumped

 

It could be your fuel pressure regulater or you could have too much carbon build-up in your intake. I have a 93' F-150 that did the same thing that you are talking about. Best of luck.