I've noticed for about the last week or so that whenever I have to stop suddenly the engine almost seems to stall out (But doesn't quite!)
I've been trying to keep an eye on the Tach, and it drops down to about 500 rpm for a few seconds, before recovering and going back up to about 850 rpm where it normally seems when idling. Any thoughts that might save me a trip to the dealer? It's an '06 LS by the way.

 

Dirty Injectors? Dirty throttle body?

 

Brake booster or line leaking causing a massive vac draw.......or maybe your torq converter is releasing late dragging the eng down....or..mabe its tired...

 

Mine has done the same, and never died until a few weeks ago. No guages came on to tell me it was dead either. Hasn't done it again.

 

i had this problem on my truck. i know a little what the problem is on my truck.

its something about air not getting in some where on your motor

 

Mine seems to have this little hiccup when it's exremely hot out. Not all the time either.

 

I had the HHR in for an oil change back in June when it had just turned on 17,000 miles. They "Suggested" then that it was time to have these two things done. I don't believe I was having the problem then, and besides, they wanted $189.95 to do the job!!
Maybe the problem is heat related too, as Deuces mentioned? One thing we have around Phoenix in July and August is a major oversupply of heat, especially this year. Don't know how they can call it "Summer", It's more like two months of HELL. Summer here is May and June, then September and October.
Anyway....I'm off topic! 99% of our driving is around town. The end of September we're taking about a 200 Mile run up North. So,I think I'll just put a bottle of Injector cleaner in the tank and hope that helps with the problem.
Maybe just running at 70/75 mph for a change, for a few hours, wouldn't hurt either.