Hey Everyone. I'm new to f150Online, but by no means new to forums. I'm having an issue with my 2007 4.6 XLT Scab that nobody at *insert other F-150 forum* has been useful in figuring out, so. . .

At 1800-2200 RPM going up hills, there's a rattling noise coming from in or under the engine compartment. If you give it enough gas to downshift, the rattling disappears. The truck otherwise performs flawlessly. No codes are coming up on the info monitor. The truck has a single inlet/dual outlet flowmaster exhaust and a K&N CAI, both from the previous owner.

 

Spark knock? Try a couple tanks of premium gas to test this theory.

 

I have the same setup on my 97 with a 4.6. I cant find the source either. My valves make noise but it sounds like its right under my feet but my exhaust and the heat shields aren't loose.

 

I ran two tanks of premium to no avail.

On the heat shield subject, where is that shield located?

 

Check to see if any heat shields on the exhaust are loose.

 

Heat shields on the cats are just spot welded and can come loose over time.

 

Ok...I had a weird rattle once like this on a hunting trip- a looooooong way from help. I thought I was throwing a rod!

Turns out it was my oil dipstick tube- bolt worked loose and it rattled like a....well, like a really rattly thing!

Go wiggle that tube...just for kicks n giggles.

I actually lost my bolt, but it turned up on the floor board of my cab- inside- and no one knew how it got there. I was way up in AZ rim country- no way was I going to find it. Truly...that was strange.

 

Since you are running K&N filters try cleaning the MAF.

 

I'll try everyone's suggestions in the next week or so. I'm also going to disconnect the vacuum 4WD system, aka IWE. Some people have had vacuum leaks causing the hubs trying to engage while driving.

 

If you disconnect the IWE vacuum system, your hubs will always be engaged. It's the vacuum that disengages them.

 

which vacuum line on the the TB disconnects IWE?