Belt tensioner problems? - or just "character"?

[gulfcat]

I've had an occasional odd low-pitched rattling noise from under the hood on my way to work, but I'd been unable to reproduce it until yesterday (45 miles short of 36000!) . I don't know if it could be the belt tensioner a friend is convinced it is, or if it's just the car's still cold, or if it's my driving:

I was accelerating in 2nd, had just put out the clutch to go to 3rd, saw a bicyclist in the road ahead, and abruptly let off the gas and kept the clutch out. Rattle! I found that I could get the rattle to happen in 2nd or 3rd (speed zone too slow for higher gears) when I accelerated up to above 3000 rpm, then let up on gas suddenly. The rattle was especially pronounced when I put the clutch out at the same time. It seems to come more from the passenger side than the driver's side up front. Once the car warmed up, I couldn't get this to happen.

Is it worth following up on?
Is the rattle normal for what I'm doing & if so, is it bad for the car?

Thanks!
Marge

[gulfcat]

Latest update: I'm very happy I pursued this!

Took a first-thing-in-the-morning ride with a tech, after the car sat at the dealer overnight, and was able to reproduce the sound a couple times (in 6 or so tries). Enough to be plausible, anyway...

The tech said it might be something to do with exhaust, since it went away as the car warmed up, and he'd put the car on the rack and take a look...

I'm getting a new "center cat converter assy" next week!

I read that as mucho $$ that just squeaked in under warranty, and I'm really glad I kept pursuing this.

(Lasik fixed my eyes, now I need something to fix my ears so that I'm more accurate about where these noises are coming really from....)

Marge