[seningen]

Were you low on oil?

You might have had a weak lifter or hearing chain noise

All hard to tell without knowing what it sounded like.

Mike

Originally Posted by Fluellen

Update:

I drained the oil and filtered it through a washcloth. No foreign particles. No intermix. Removed the filter and cut it open - nothing. Looks exactly like the previous three filters I cut open.

Re-filled with Rotella 5W40 (same as before; last oil change 5 months / 1 Kmi ago) and started it. Smooth idle, no noises.

I haven't checked for noises above-idle yet (all engine covers are off, and the motor gets quite loud when you go >1500 rpm).

I guess I'll look at the spark plugs tomorrow, just in case.

Is it possible for a valve spring to be broken, and you can't hear it at idle?