Rattle at Low RPMs around 1200-1800

[timjamz]

Hello, all! New owner of a used 2007 base sedan with manual transmission, about 130K miles on a replacement 1NZ-FE engine.

I am getting a rattle in the top of the motor (pretty sure timing side), at low RPMs around 1200-1800. It happens under load (i.e. clutched and accelerating) or revving free, but more noticeably under load. The rattle does not happen at startup like a typical loose chain slap. RPMs do not fluctuate abnormally. Idle is good, but perhaps a little low around 500 and shakes ever so slightly. I have done the following:

- Replaced spark plugs with the recommended Denso iridiums.
- Cleaned the VVT solenoid and screen (both were in good shape but cleaned anyway).
- Cleaned the PCV valve (I did notice it does not close all the way sitting loose, but it does have *some* spring tension and blocks air only one way as it should).
- Changed the oil with Valvoline synthetic 5W-30.
- Added octane booster and filled up with 93 octane.
- Flushed the clutch line (and whole brake system) with new DOT3.

Still the rattle persists as described.

Googling and ChatGPT suggests the VVT solenoid may still be failing, the chain tensioner could be failing (why did they move it inside the timing cover on this model?? ), or the VVT sprocket could be failing. It also suggests exhaust or similar rattle due to worn motor mounts as a possibility, but that seems unlikely to me and doesn't sound like it.

Before I throw parts at it, do you all have any experience with this issue? I don't mind replacing the VVT solenoid and PCV valve, if those could be the culprit(s).

Thanks for any feedback or advice! I would love to get 300K+ out of this engine, and the vehicle is otherwise in great shape and drives super smooth.