yup. IAC.

I would start by giving the truck a tune up. new plugs, wires, cap, rotor, and clean/replace sensors, clean the TB and IAC port, etc.

then, reset the computer (unplug battery overnight)

the IAC function is a learned aspect in the computer programming. the computer learns/remembers what settings the IAC needs in various conditions to keep the engine running at the target idle speed. If these conditions begin changing, the computer doesn't know what to do and freaks out.

now, some noise is to be expected, did you guys recently change air filter/intake systems? you may be hearing it more now because of such a change.


if your belly pan gasket is blown/leaking, you won't hear it. but you will have excessive oil consumption and pinging under WOT from the oil getting sucked through the intake. it's bolted on, not riveted, and many have found that the OEM/factory bolts are too long for the tapped holes, and don't allow you to fully tighten down the plate. washers stacked on the bolts eliminate this problem.