So my '04 ticks like a lot of others. It's quiet when cold, and when the engine is warm it goes away about 2,000 rpm. No other issues.

I dropped it by the only foreign car shop in town, and they figured it was the "flapper valves" in the intake manifold that were slapping at low rpms. Apparently these valves control the plenum length. $1,700.00 to replace the manifold.

Anyone heard of this problem with "flapper valves"?

 

At idle they really do not matter. Suspect these are the ones that change the "tuned" intake tubes from low speed (longer) to high (shorter). Before there was VVT this was a kludge to help spread the torque band.


Unless you are under load so near the torque peak they do not do much.


Can anyone confirm this is what makes a tapping sound sometimes.

 

$1,700 buys an awful lot of ear plugs.

Frankly I'd say BS.
If it is loose it can be tightened up without buying a new manifold. It can't be rocket science here.