I wanted to update everyone on the HHR's status. I decided to just take it to a dealer since it was likely something internal to the engine (i.e. warranty) and no amount of troubleshooting on my part was going to fix that, just diagnose it.

So we dropped it off at the dealer, they checked it, found the exhaust valve on cylinder #3 was 'burnt', and sent the head to a machine shop. Did a test drive and found no issues. Zero dollars, only out of the car for a few days, and we're back up and running. Not bad.

Now, what, if anything, can I do to prevent this in the future? If it's just a poor design, can I expect this again in 20k, 40k, 80k...etc? I've purchased a leak-down tester so I can troubleshoot next time.

 

I've not heard of this being a common problem. Have dealt with three HHRs including ours, each of which had/have differing mileages. Ours was at roughly 60k when we sold it, my nephew's has roughly 85k on it, and my niece's had 176k(!) when she sold it. None of them had a burnt valve at any point. Perhaps you were just 'lucky' enough to get one that didn't properly seat after assembly.

 

I'd be willing to believe that we got 'lucky,' but the tech who I spoke to seemed to indicate that it was a known issue on Cobalts and HHRs. Maybe it happens to Cobalts and HHRs assembled late on Fridays.

 

If that's the case (known issue) then we dodged the bullet three times! Three differnt types of use. One was driven fairly easy, one moderate and one hard; none of them had that problem.

 

Seems to be always #3. There must be a reason.