Ok my in-laws bought a 2010 HHR from the dealership my wife worked at about a year ago. It has always had an odd sound when starting. I would say it sounds like a rattle similar to if you put 3 to 4 rocks in a soda can and shook it. The sound gets louder when accelerating but is always there. The vehicle seems to have no performance issues that I have noticed other than that and we have to replace the soft clothlike intake hose. Any suggestions on where to start on checking this rattle sound?

 

Rattle at start up,

timing chain tensioner
upper engine mount , toast!
broken air cleaner box bracket.

just some possibilities, check those.

 

Maybe record it for us.
Or....

 

We actually had an instance of "it was a RC cola cap stuck in the alternator", after a long thread.
I would suggest opening the hood while the noise is going on and trying to narrow down the area it is coming from. Don't need anything other than eyes and ears to do that much.
If there is a strange odor in the cabin it could be the flex pipe is cracked (deadly). Mine smelled like solvent not exhaust.

 

What's the trim level? LS, 1LT, 2LT, SS?

How's the engine oil level?

 

it is an LT and the oil level is perfect, we actually change them all at about 30% life left and all are on full synthetic.

 

The flex pipe (wired cloth from fender to air box) is broken and been removed, told them to buy a new one but they haven't yet. It sounds like with the hood up it comes from the front of the motor dead center, just can't tell if it is top or bottom of motor. Other than that it seems to be acting normal too.

 

RECORD it. Also, record it while doing a snap throttle..

 

Flex pipe is the accordion bit from the exhaust header to the exhaust pipe. They crack with regularity as a result of worn motor mounts. Dead center in back of engine.
You can replace the cold air intake hose with a bit of metallic hose from Home Depot.

 

This what the flex pipe looks like. You are speaking of the woolly worm that bring cold air in from the inner fender