Drove the car a few times since the noise appeared. Thanks goodness the noise has not returned.

I took the Boxster out to clean out all the cobwebs. I drove out and up Azusa Canyon, an area of gentle twisties. She ran awesome, an usual. About 2 hours round trip from my home.

Yesterday, a week later I fired her up again to get some groceries. When she started, I heard a rod like clunking noise that disappeared after 20 seconds or so. I assumed it was a stuck lifter and commonplace? She ran great after the start up.

Thoughts?

With a car of that age you might be starting to get some clogs in the lifter oil channels. But that would make a ticking sound on cold start, not so much a clunking sound. Maybe record the sound?

If it is lifters you can try running some lifter additive. Note that there are a few different types that have opposite effects (definitely don't want one of the ones that increases viscosity). I've had luck with Liqui Moly 20004 Hydraulic Lifter Additive. The Boxster requires about 1½ cans.

Thanks. That one time was the only time I heard it. I be ready with my phone to record a video on the next start up, if the noise returns (I hope not).

I suspect that it occurred because I drove it harder than normal before putting it to bed.