Ok, so I cleared the P1174 code, 200 miles later code came back, cleared again, about 200 miles later, got p0300 along with p1174, sounds like its getting serious, still seems to run fine, but I will ask a buddy to do a comprehensive scan with a OTC Genisys,
I put my Autoxray EZ-Scan 5000 on it and ran a diagnostic, it shows a data stream and the front O2 sensor is all over the map, nbrs are just a blur, until i accelerate a bit, then it reads .7-.800, rear O2 is steady around .7-.800,
FWIW, a little history, car has had a Weapon-R cold air intake since around 12K miles, car now has 107K, and is burning oil, about a half a quart every 500 miles. Also has the same spark plugs since the cold air intake was put on, only use premium fuel, car has good power, but sometimes accelerates kinda sluggish and wont downshift.
On a previous repair for a throttle body CEL, I cleaned the throttle body, it was pretty gummed up, and there was fine dirt particle build-up present in the intake and throttle body,, IMO, I dont think the filter on the weapon-r is doing a good enough job filtering out fine dust particles.
I live in a rural area and my drive way is a 1/4 mile dirt road.
Other than that, I love the car

 

#1 O2 sensor is supposed to be all over the place, the faster the better. However, it should not go above .9 or below .1. You need to graph the outputs.

http://engine-codes.com/uploads/gmc/03-06-04-030F.pdf

Most likely bad injector(s). I recently got 4 new GM injectors for my 2011 2.2L for $88 shipped from China (in 6 days).

 

Ok, good, then 02 sensors look normal, Did u have the same code? I looked on ebay and found these:http://www.ebay.com/itm/301366339355?_trksid=p2060778.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

 

I had P0420. Injectors cured it for now.

There was a year that required replacement injectors to be genuine New design and a reflash. There is a TSB.

 

i put the stock air cleaner back on, i also removed a catch can i had put in place of the pcv line. i used a small a/c receiver/drier, but i found what looks like brown water in it, it was about 3-4 ounces, i thot that was peculiar. so much water vapor?? could that maybe explain the p1174 and p0300, ? where would so much vapor come from? radiator is full.
i disconnected the battery and let it sit for about an hour. so far no cel, see what happens over the next few hundred miles.

 

Sounds like combo of burning oil and some coolant. And yes could be the cause.

 

I have a 2007 HHR with the check engine light that's been solid for about a month. Before that it would go on and off. I'm getting codes P1174, P0300, and P0302. These indicate fuel trim imbalance and cylinder misfires. Based on the service bulletin it looks like you need to replace all 4 injectors and reprogram the PCM otherwise the problem will re-occur. To me that sounds like the previous programming caused the problem.

 

I have located a good used motor just in case, but as i have been pouring oil thru this thing, i notice on the underside of the oil fill cap, that dreaded milky film. weird thing is my radiator is full, dont have a lot of money to throw at it, so, will do a compression check and see what i find,

 

Ok, as Paul Harvey used to say, "Now for the Rest of the Story",
My wife and I celebrated our 35th wedding anniversary and drove from Fresno Ca, to Las Vegas, in our beloved HHR over the past weekend.
I knew there was this minor problem, p1174, well,,,and excessive oil consumption. So I drove about a 100 miles to bakersfield and stopped for a pitstop,, checked oil, it was more than a quart low,, hmmm, added oil, topped off fuel and back on the road. Stopped at Kramer Junction outside of Mojave as in DESERT, again, quart and half low. so burning or losing about a quart and a half of oil per 100 miles. Arriving in Las Vegas we came off the interstate and stopped at the light, car dies, have to drive with both feet on the pedals to keep idle up,, found excessive blowby was screwing up the maf,, Got the dreaded Low power display and rpm was limited to about 2k,, so I rerouted the pcv line from the head to the oil fill spout with a half inch hose, just stuck it in the spout all the way down, so all the vapors wont contaminate the maf sensor, and i plugged the hole in the intake hose,, i was able to get it home that way, ran better, but it took about 10 qts of oil to get from Vegas back to Fresno. Later today i will chk a few things including compression, but here are the codes fwiw,, P0011, P0068, P0172, P0300 and P1174, I think I have a hole in the #2 piston myself,, but time will tell. As I mentioned I have a line on a used motor from a low mile wreck, and luckily I am capable of doin the work so not too concerned at this point,

 

Some of those codes are from moving the PCV hose.
P0300 is random misfire, fouled plugs.
P0011 is the camshaft sensor/solenoid thing, could be from low oil.
P0172 is too rich, can mean a lot of things including fouled plugs.
P0068 is the MAP and the MAF not agreeing.
P1174 is usually clogged injectors.

Why do you suspect #2 being a problem?