2008 2.4 with 100,000 miles.
Three weeks ago we had the misfire codes,MAF sensor code and the MAP code come up. Found the spark plug holes had oil pooled in two of the holes. Changed the valve cover gasket checked the chain for play,found none, and replaced the plugs . Found my throttle body very badly caked with carbon and thought after cleaning it properly it was still not really clean so I replaced throttle body with a new GM T/B. After the relearning cycle the car ran great.
Took car on 300 mile run and sadly we ran the car under the 1/4 tank threshold and filled up with the LOW FUEL light on. Now the car is studdering at highway speeds dropping 500 RPM's @ 70MPH. Not constantly but enough to know something is happening that is not good.
No CEL is showing.
I'm thinking we damaged the OG fuel pump. I have not checked fuel pressure yet but will before I throw parts at it. We are driving out the 3/4 tank of fuel so I have a couple days before I'm crawling under there to change the pump if necessary so I have time to discuss this!
4th HHR and we never lost a fuel pump yet so I'm not sure if they go out with a sputter or just quit completely so any thoughts are welcome and I will follow up with the final answer when I find it!

 

Where did you hear anything about 1/4 tank threshold? I have run literally dry several times with no damage done, no overheated pump, no lost prime. Water settles to the bottom of the tank the pickup is at the bottom of the tank. Old wives tales, your HHR was made this century.
You might want to simply check the fuel pressure, most big box stores will either loan the gauge or buy and return.
Not all codes light the CEL, you should get live readings when the the problem is happening.
What cured the MAF and MAP codes? Nether of those have anything to do with plugs or TB, more likely somebody didn't plug the MAF in properly after a filter change.
The throttle relearn is simply idling for 5 minutes, nothing magic.
Do you mean the RPM drops by 500? Like when going up a small hill not enough to downshift? That would likely be a vacuum leak, maybe the brake booster tube or something that got dislodged under the hood.
If you did not use ACDelco 41-103 Iridium plugs that might be the problem. They are good for at least 100,000 miles. Do not try to set the gap, that will break the whisker.

 

ACDelco 41-103 Iridium plugs were put back in.
The stumble is 500 RPM on a flat highway and it's not a shift related stutter, the RPM drops instead of revs.
I had thought there could have been water in the bottom of the tank or even a bad gas situation so I wanted to ask before I jumped into a diagnosis of the pump being bad.
The fuel pressure gauge was loaned out at the local parts place so I'm waiting for it to return and will get readings soon.
And the code reader I have was at the house so I couldn't plug it in during the ride to see if there are hidden codes. Will plug in and re run the car for verification.
The low fuel theory has been shared many times on this site. And this is only the second time in 3 years we actually got low enough to light the low fuel warning so it made me wonder if there was any truth to that theory.

 

And the codes cleared after I disconnected the battery and had a shop with the good GM code scanner hook it up. they found no new or hidden codes.
And yes,the plug on the MAF was loose after an Quick Change place changed the oil but that was separate from this incident .

 

I don't recall ever seeing that on this site in relation to the pump. My wife is paranoid about under 1/4 tank for fear the gauge is wrong. I have found that there is almost exactly 100 miles left when the low fuel lights up.
Some of us old fogies remember the tales from last century and assume they are still valid. I remember warnings about fuel injected cars losing prime from letting the gas run out, might have been true back then, after all diesel fuel injectors loose prime.
The pump does not normally catastrophically fail. Usually there is hard starting or fuel trim codes first.
Dropping 500 RPM is about what should happen when engaging OD/4th gear or the Torque converter clutch. Have you noticed a drop in MPG.
What fixed the misfire, MAF and MAP codes, what were the actual code numbers? Code names or descriptions are completely useless.

 

There's been discussion of fears of overheating the fuel pump, that it is kept cool by the fuel. I don't recall anyone attributing a failed pump to running out of gas. Just fears.

 

Check the fuel pressure when you can get the test gauge . Go from there.

 

Local parts store did not get their gauge back yet. Will go to another location in the AM.
Took car for test drive and it stumbled once then ran right. Will drive this tank out like I posted in the beginning of this thread but I am hoping we just got some bad gas. Wife said she put 87 octane in it. I always used 91 octane. We will see what happens next.

 

In regard to octane; have you read your Owner Manual? 2.4L is recommended 91 if it pings but runs fine on 87. 91 is overkill unless it is only 4-5 cents more then the added MPG might be worth the price, otherwise wasting money.

 

Just looked in the 2008 OM. 91 is recommended for the 2.0 and 2.4.