2004 F-150 Heritage 4.6L V8 4X4

All right, first off this noise is pretty difficult to explain (as any noise is I guess). It's kind of a quick chirp, hiccup or burping sound coming from the intake.

It does it when I first start-up, sit at idle or when it's coming down from letting off the throttle (more noticeable now that it's cold out). I can hit it wide open and it'll do it real good when I left off.

When it happens the idle will surge up to about 1400 and back down. When driving I do not hear it but it does this at a stop light when holding the brake it seems to try to lunge forward a little forcing me to press the brake harder.

I have a CAI with a AEM dry filter on it. I removed the filter and ran it to see it it would do it and it does. I took everything off, cleaned the throttle body and MAF sensor, didn't help. I read somewhere else it could possibly be the pcv valve gummed up. I shook it and it seemed good, but replaced it anyway to no avail. And before anyone says anything about fram oil filters I use motorcraft.

I haven't noticed any difference in performance, throttle response or driving it's just annoying as hell and doesn't sound too good.

Any ideas?
Thanks in advance!

 

Just guessing here as you don't mention any codes. I'm wondering if its your IAC ( Idle Air Control) and when the RPMs increase while at idle the serpentine belt is making a chirp noise. IAC's control the idle and serpentine belts do chirp sometimes when RPM's are increased.... Also make sure that the intake tube where it fastens to the throttle body is completely in place over the throttle body and the clamp is tight. All vacum lines are connected with no broken lines, elbows, etc?

 

Sorry, there are no codes. Scanned just in case. I'm pretty sure it's not the belt. You can hear the noise actually echoing out of the intake tube. I've checked for any broken, cracked, torn, disconnected vacuum lines and have found nothing wrong. The intake is fastened securely to the throttle body as I've removed it twice to clean.

The CAI itself is about 4 yrs. old and was basically dirt cheap when I bought it. It was from 4Wheelparts and never quite fit right. But I've never had any problems with it other than the crap filter that came w/ it. That's why the AEM is on there now. As an extra measure and the fact that I'm getting it free through work I'm replacing it w/ a Volant system.

I guess I'll try cleaning the IAC and see what happens.

 

Well, cleaned the IAC to best of my ability and it didn't help. Other than the new intake that's on the way I guess my next step is possibly replacing the IAC.

Also, as an update to the description of the sound, when I hit the throttle pretty hard and let off the chirp is almost like a stutter. Da, da, da, da, da...and the engine surges.

 

I would hold off on spending $ 60.00- $90.00 for an IAC just yet. Do you have the original stock intake system laying around, zip tube, etc? If not maybe borrow one from a buddy stick it on and see if things change? Sounds like it might be related to the system you have installed right now. I don't know I'm just shooting in the dark on this one. I was thinking your idle was ramping up fast but sounds like the noise is more on deceleration.

 

almost sounds like a miss. i know when i had a miss i could feel a burp /Lean pop back out the intake i could feel it threw the gas pedal. changed the plugs and never had it again.

also my IAC was making more of a humming noise when it was dirty.

kinda sounds like it could be a vac. leak check PCV hoses and what not for leaks.

 

mine makes a similar sound but it doesnt feel like its surging...and i dont have any codes showing up...its more like a tinny da....da,da,da,da..da.its freaking annoying...

 

and its normally at idle but have heard it decelerating from around 45

 

Ok this noise is annoying!! I dont know what the hell its is and it seems like its coming straight out of the throttle body...

 

I ended up replacing my CAI with a Volant system (was going to prior to this noise anyway), thoroughly cleaned the throttle body, and replaced the IAC valve. At first I could swear it was still doing it, just a lot quieter and didn't surge. But that could be because the Volant sealed CAI was muffling the sound. Recently, I replaced all eight spark plugs and not a peep since!