Hi all,

Recently my 2011 HHR has been rough idling. I do not notice any issues when my foot is on the gas, but as soon as I begin to decelerate, I start to feel the vibrations and rough driving. Then once I get to a complete stop, my car has a noticeably rough idle. The check engine light recently came on and only showed a P0300 with no other codes. Granted I only have a small pocket scanner at home and not the big computers they have at most repair shops. I changed my spark plugs and the ignition coils yesterday, but as the day went on, I noticed that it didn't help. The rough idling wasn't as rough immediately after the repair, although it was still noticeable to me at least. But it was more than noticeable by the end of the day.

I have compared the symptoms to the list of possible issues related to the P0300. I have no issues with the car once I get my foot off the break and on the gas pedal. I have no issues driving the car at highway speed. Last night to test out a theory I put some fuel injector cleaner in the gas tank and it seemed to run normally for a few minutes. This is leading me to believe I have a faulty fuel injection system. What do yall think?

 

Did you use AC/Delco 41-103 Iridium plugs?
Compression test needs to be done.
P0300 lights the CEL when the catalytic converter is in danger.
Is the AC compressor clutch working? Is the defrost on? Is the AC on? The compressor runs in defrost and recirc with no warning light.
Any vacuum leaks?
Recent air filter change? The MAF doesn't get plugged all the way sometimes.
Doubtful the coils are ever involved.
The "big" computers are only good for interacting, they get the same diagnostics as a $10 tool.

 

I'd have to check the packaging when I get home from work. I have had the AC and defrost on in the last few days with no noticeable issues. I have not noticed any vacuum leaks (no issues accelerating, no high pitch noises from the engine). I personally replaced the air filter a few months ago, and the MAF was also replaced a few months ago as well. I will double-check the connection of the MAF later today to make sure it is secure. I only changed the coils because I changed all four spark plugs. I figured it was best to change all four coils as well.

 

Anything other than AC/Delco 41-103 Iridium plugs are not reliable, they last at least 100,000 miles. Do not try to measure or set the gap.

 

Try cleaning the throttle body , use throttle body spray cleaner from CRC do not try to move the butterfly plate just squirt the cleaner on the plate, remove the four bolts and spray the engine side if it’s really dirty.
P0300 is a generic misfire code , it doesn’t specify any specific cylinder is misfiring.
you can also reinstall your original coils if you still have them. See if the engine responds better, then you can return the new coils.

 

so driving home from work, the car stalled on me no less than 4 times. The check Engine light came on again but this time it game me a p0011 code, which makes more sense with the rough idle and the rattling noise coming from the engine. I attached a video I took while idling at a stop light on my way home.

 

Video ? Don’t see one.
P0011 points to a VVT issue. Possible actuator solenoid. But, a rattling noise could be serious. Timing chain failure may be near. I would park it until you figure out what that rattle is.
Continue to drive it, you risk engine failure.

 

I am guessing timing chain issues.

 

Let me know if this video doesn’t work. Otherwise I can text it to someone

 

You can’t post videos straight to this site. They have to be hosted or whatever it’s called at some place like YouTube. You then post a link to the host sites video location.