Do you let your hhr warm up?
 

I let mine get go 150-190f. So far 192k miles and no motor issues so far. I also drive like a grandma 90% of the time and rarely get to 3 or 4k rpm.

Yeh, for about 5 seconds.
173k and no issues.
I too do not drive 'hard'

Absolutely.. In winter, I leave the DIC set on engine temp, & start & pull out of garage & let it idle till it hits 100* & then ease on down the road till it gets up to temp.
Then I drive like a normal nut.

For Sure especially when the temp is below 40 degrees F.
Idle for about 3 minutes then easy throttle for about 3 miles, then normal driving unless some AbNormal Nut tail gates me.
Most of the HHR's I have owned have a little lite rattle/knock noise with any pedal pressure until they warm up .... then gone..

Silverfox

I'm about the same as sleeper.

I only let it warm up as long as it takes me to get my items arranged. Mine hits 180F in 3-4 minutes anyway.

A 1 minute warm up, to get the oil and coolant circulating, then a slow roll out of the subdivision and normal driving after that.

kinda just get going BUT I live on a hill and cost down about 3/4 of a mile to level ground so technically I am idling for several minutes.

No real warm up here, by the time i hit the end of the driveway and then end of my
street. I have put put 60K on top of 50k, and no troubles.

Here in NorCal start and go is my routine.
However I am searching for a vacuum leak or a cause of rough idle when starting.
Replace air filter cleaned throttle plate and MAF.
When in Oregon few weeks back was very rough start at below 28 degrees and frozen and had to feather throttle a bit to keep it going first 30 seconds.
Check plugs next.
my climate control door is still flapping on start as well. Search on that reveals the procedures Thanks