2004, 2.4L (non-turbo) Valve Chatter.

[Jabouty]

Background:
Chatter started about a year ago, a very light tap tap tap noise on the passenger side, near the rear of the valve cover, it has become progressively louder over time. Pulled the valve cover to inspect rockers and lash adjusters and found no obvious chatter points, no loose valves, everything was tight with no spacing, nothing to concern me over.

Fast Forward:
Last month timing slipped teeth at idle. The tensioner had gone bad. Had baby towed to my mechanic's shop and sat overnight. Mechanic replaced belt, tensioner, idler pulley, water pump, accessory belts and rocker arms (since he was in the engine already) and cleaned the lash adjusters and found no issues with them at all.

Fast Forward abit more:
Any temp, any RPM above 1800, especially under load, valve chatter is loud enough to be heard within the passenger compartment, windows up. It sometimes disappears completely, but only for a few minutes of driving.

I have experienced no gas mileage issues, the PCM is giving no codes at all through the tester or the dash check. I have noticed that she's losing oil somewhere though over the last couple weeks. She's not blowing blue smoke, and there's no oil in the antifreeze that I can see, and there's no obvious oil spots on the concrete when she's sitting over night.

I'm suspecting either a clogged / bad oil pump, as the chatter does disappear at around 3k RPM, or a head gasket allowing for slow oil burn. The chatter does not go away when I refill the oil however.

Before I tear down that far, does anyone else have any ideas or thoughts on this one?

Cruiser Specs:
2004 Limited Edition
2.4L DOHC, non-turbo
115k Miles
24 MPG average at the pump
P205/55R16 Tires / H Rated (forgot manufacturer...)

Thanks!

Jab

[Jabouty]

LOL. Stumped the experts too? I don't feel so bad now.

[bobdole369]

Fuel injectors are very loud and make a tapping sound. Could that be it?

I keep thinking both my PT's have valve chatter, but recently had the older one in for a timing belt change, and no sign of it anywhere. The mech replaced the valves as part of it (valves hit) and no sign of any play on the lifters or the rockers. Was told by that guy that the fuel injectors are what I'm hearing in the engine compartment. Confirmed at ptcrew as well as this forum.

From what I hear the hydraulic lifters sometimes need adjusting on some PT's. But you seem to have addressed that.