I just noticed a rattling at idle(intermittent), seemed to continue up to 30 mph, but, could not hear after that. Got home, under hood. Doesn't sound like belt tensioners, at least not when I get close. Sounds like in back of engine, near end of exhaust manifold, in the general vacinity. Will go out, park on curb, and check exhaust from underneath, but, I do not think thats it, sounds different. Ideas anyone? Thanks in advance. On the road to 340 mile trek to work in the morning ... \
Well, just under car, can't indentify it. Sounds like a hamster wheel type of noise. Raised idle(1k), little change, than gone??? Definely not near belt tensioners. Also tried adjusting speed of blower fan in car, not that either. Can hear better in car, near passengers foot well???

 

Do you think it might be associated with cat convertor? I experience same with mine which is an automatic. Once I experienced the same with a GM of mine with over 100,000 miles on it. Removed cat convertor problem solved, but these days it isn't so easy to remove convertor without a whole host of other issues. How many miles do you have on your machine?

 

The noise is not associated with the cat. I sounds as though it's under the exhaust manifold. Closest I can relate to is, hamster wheel, mild clicking, almost like the interior fan motor, squirrel cage. I ran the fan and no difference ... ?? Sorry, mileage, abt 250k, still hits 105mph ok though. Odometer broke at 178k quite aways back ,,,, that's on my to-do list, not urgent ..

 

well, I've kinda determined it must be exhaust. I asked a trained professional(girl friend with better hearing) to listen for it, right under/behind exhaust manifold ... as Gilda Radnor would say, "NEVER MIND" ... while looking in the area, I did notice the old heater hoses, that I've never tended to in the last 9 yrs of my ownership ... that is on the to-do list

 

I had something similar with OBX band clamps. The exhaust would rattle at specific RPM. I dunno if your running an aftermarket exhaust but the concept would be the same.