I have a high mileage HHR, 160,000+ miles. The car has lost power to the point where I could barely make an entrance ramp on the Interstate. This was a gradual loss over about 2 years.
Fuel pressure was OK, I checked that first. Next I replaced the injectors, which was easy. No change in power. I suspected the throttle body could be on it's last leg, so I replaced that next.
No change in power, and now it had a slightly erratic idle. Sometimes when slowing the idle would go up to 1000 RPM and then gradually settle back to normal. I did the learning procedure correctly, so that wasn't it.
Out of desperation I removed the gas pedal assembly (APP sensor) and took it apart for cleaning. It looked good, but the human eye cannot see electrical resistance. I reassembled and installed, and did the TPS relearn again, since they are tied together.
The engine ran like it had 30% more HP, when it was actually just the throttle body opening like it should. On my test drive I actually had to back off on the gas in situations where I had previously floored the pedal. The erratic idle is gone, too.
So that was it, the gas pedal. It acted like there was a rock under it, cleaning the contacts removed the rock.
The procedure is easy, so if you have an HHR with high mileage, you may want to do this cleaning. A new pedal assembly is around $135.


Remove 5 screws to expose the contacts. Clean with electronics cleaner.

 

Good tip, thanks for sharing

 

That perspective is wild. Took me 10 minutes to figure out why you were showing us a lift tongue.