Coil pack, ac 41-103 plugs, ignition module and new boots replaced. Afterwards code p0302 switched to p0300. It then went to p0303 and after a few minutes it switched back to p0302 again. Have read articles where dealership sometimes reprogram software or update. Don't know if this is a probability or not. Just looking for feedback. Going to clean maf sensor tomorrow as I saw if it is dirty it could cause a lean misfire. Also watched a video where a vehicle had a battery that would start but then not enough juice to power electronics causing a possible misfire. My battery is borderline weak as I tested it today while negative cable disconnected. It is an autozone gold purchased 9/21/11. The possibilities seam endless and the dealership will only get a crack at it after I raise the white flag and I am not one to give up easy on anything.

 

Also gas cap replaced as a curiosity as this all started in spring. Got code p0302 and after running red line fuel additive hhr was good to go until around the end of September. I stopped for gas one evening and the next day was when mil came on and with wife needing radiation treatments I could only do so much because we relied on it to get to appointments. Couldn't afford to be without wheels so just babied it along until now.

 

Why not go back and read the suggestions people have already left for you before you start messing with the MAF sensor? You can screw the MAF up real bad if you don't clean it properly.

You say you tested the battery is "borderline weak" - how did you test it? Putting a volt meter on it is one thing, testing it with a proper load-tester is another.

 

TL, I've read hundreds of threads, thousands of posts since (and before) I joined up here. I try to read every word of every post, there may be a tidbit that got mentioned only once, but was spot on. I've learned that these guys offering suggestions here are great troubleshooters. And not to slight anyone else, but Donbrew is exceptional. If he suggests you may have a problem with the fuel delivery system, you'd be wise to look into that.

But I get that you want to check things that cost little to no money first, nobody is made of money. You may want to spend some more time with your friendly neighborhood search window (at the top of every page). You're right, vehicles have gotten very complex, and the potential causes are numerous. The thread I linked to, the fix was a new fuel pump. Another thread said a new battery fixed it. Another fixed the problem by replacing the timing chain. Another owner said he finally discovered the problem was that it was low on oil by 2 quarts!

I hope you find the fix.

 

cleaning crud out of the fuel rail would be free!, just disconnect it and flush it.

 

We all try to reach out with the inexpensive first, and it can be confusing and frustrating when the one thing doesn't work, but hey we are here for you, I always will be willing to research for those that possibly don't speak HHRenese! Whopper and Donbrew do and fluently as many of our members do.
What is most unfortunate is many new members will ask a question and then not return to confirm anything we suggested fixed their problems.

 

Oh, by the way fuel system was tested with a pressure tester and it shows 70 lbs at idle with no bleed off. Thanks

 

The fuel system could still be dirty, the check valve is over by the inlet to the fuel rail, by #4 injector, away from the rest of injectors inlets, dirt and crude can cause havock , have a look at the picture in this EBay ad.

http://m.ebay.com/itm/OO027-FUEL-INJECTORS-WITH-RAIL-SET-ALL-2011-CHEVROLET-HHR-2-4-/151884412615?nav=SEARCH

 

The crud floats in the rail, when you turn it floats and clogs the output hole.

 

Scanned hhr after running some errands today. Now reads p0300 and p0341. Car runs like the wind. No backfires, stumbles or cylinder drop. Hard to believe mil is on and not out the way it performs. Have read all posts and gone over previous work to no avail. Appreciate all help you fellows have given and I'm positive it has to be something simple that is staring me in the face. Just can't put a finger on it. The battery was checked with voltmeter, then under load, and then under load with voltmeter attached. Reading was approximately 10.6. Ran GM top engine cleaner today also as it was near a quarter tank. About two gallons left in fuel tank right now before empty. Thank you again for sticking with me. 64 going on 16 and have been car nut ALL my life. Trying to keep up with new technology but I'm afraid the gap is beginning to widen a little.