Here goes. '05 Lariat Screw 5.4 4x4. When I start the truck I here a strange noise that sounds like a vacuum leak that fluctuates and then fades away after a minute or so of idling. The noise is much louder under the truck right by the trans. But I can't find the source. Also when I shut the truck off I get a very annoying sound of vacuum from the intake/air filter housing. I found that if I remove the vacuum line on the passenger side that goes from intake to valve cover and plug the the vacuum port at the manifold, the sound is gone on shut down. The truck has never done this in the past!

I have searched for roughly an hour or more and have found a lot of info regarding the 5.4 2v related to cleaning the maf, 02 sensors, bad pcv elbow etc. I realize these can cause a p0171 as well on the 5.4 3v (except for the pcv elbow at the back of the intake) but not much else on my situation.

Any thoughts/input would be greatly appreciated!!

Thanks in advance ,
Ed

Got some lookers, any help! Please!!

 

P0171 Bank 1 too lean

Do you have an aftermarket air intake on the truck? Are any of the tubes on the intake disconnected?

 

Freeky, thanks for the response. No CAI, mods are: E-fans, maggie SISO, K&N drop-in filter and the Edge. All have been on for 35k miles or so. I recently replaced plugs and fuel filter, FOMOCO parts. Any other thoughts? I'm thinking I may have a stuck solenoid some where in the emissions/evap system. *shrugs*
Any other thoughts? Oh! And along with the p0171, the check engine light just came on however no new codes. Any idea on how to check the solenoids?

Thanks,
Ed

 

ALL for the "OVERWHELMING' responses . A little sarcasm, you bet. freekyFX4, thank you for your help my hat is of to You.

Problem with p0171 resolved!!

Ed