2011 HHR LT throwing a P0172 code. I understand what it means, just looking for the most common cause. Vehicle has about 54000 miles.
Any info would be appreciated.

 

Unmetered air getting into the combustion chamber.

 

Thanks for the response, so basically a vacuum leak? If so where should I check? I did pull the air filter out, cleaned the MAF and checked what lines I could see but was unable to find anything.

 

Anything between a hole in the EVAP pipe to a cracked flex pipe.

 

Thanks again, I will check both.

 

A code P0172 may mean that one or more of the following has happened: The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters can cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry. There could be a vacuum leak. There could be a fuel pressure or delivery problem Possible Solutions Possible solutions include: Inspect all vacuum and PCV hoses, replace if necessary Clean the MAF sensor. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling Inspect fuel lines for cracks, leaks, or pinches Check the fuel pressure at the fuel rail Check the fuel injectors, they may be dirty. Use fuel injector cleaner or get them professionally cleaned/replaced. Check for an exhaust leak before the first oxygen sensor (this is unlikely to cause the problem, but it is possible)


The most common denominator is a cracked flex pipe, if your exhaust is louder then normal


https://www.chevyhhr.net/forums/prob...-please-60572/

 

Bumping this thread. 2011 HHR 2.4L with 162,000 miles. Just got a P0172 code I have been chasing for a few days. Here is a list of what I checked.
Purge valve under the hood I could not blow through so it’s good from what I read. Can’t find any vacuum or exhaust leaks. O2 sensors were replaced 60,000miles ago, scanned the engine and looked at all the values running and not. O2 sensors looked fine, all fuel looked fine. It was time to change my air filter and spark plugs so I did. Cleaned maf sensor, it and map and IAT all read good. No compression issues.

Here is some info about the HHR. I only drive it 6miles a day five days a week. It doesn’t see full operating temp I’m almost positive in such a short low speed drive. Locals here have been having issues with a gas station I just have happened to be filling the HHR up with not our other car. A bunch of people have had engine issues, either alcohol in the gas or water. So I bought a bottle of HEET and added to the fuel tank I already had.

Have done a lot of reading about alcohol levels messing up flexfuel cars, that and fuel trim levels need to be set back to zero. Not sure my buddys scanner can do that. With new air filter and plug change it starts great and doesn’t chug but did notice after sitting 12 hrs and it was 66 outside this am it started right away just maybe kinda reved down quick?? Before it was a weak start then kinda rough idle then never again unless really cold.

So this am it was 66 degrees and I drove it for alittle over 3hrs. For several miles on a highway doing 45-60mph and giving it good joints of the gas pedal and it ran great. No smoke from exhaust from the so called rich code. Only thing I noticed is at that temp out and me getting on it to 80-90mph the digital temp only read 169 the highest. Then I came home for a few mins left it running and go in. Temp read 212. Went 20 miles away and left it running in a parking lot and watched the temp go from 170ish to 217. Then it slowly went down to 170ish. Then driving back home again it stayed at 170ish with outside temps at 69. I have read coolant sensor can cause P0172, and thermostat as well.

Does anyone else think my cooling sensor or thermostat might be the issue with the colder starts? Engine reads a different temp when key is turned and adds more fuel…

I did notice with plugs and air filter exhaust smells cleaner out the tail pipe.

Thanks for any help! Also gas mileage is not being affected at all.

 

170 degrees indicates the thermostat isn’t doing its job. If you have to change the thermostat then drain and change the Dexcool, it has a 5 year lifespan.
I’m sure you’ve read about the thermostat, only install an AC Delco 131-158 , 180 degrees F . And burp the coolant to ensure no air is trapped in the system.


https://www.chevyhhr.net/forums/how-...l-p0128-24493/


https://www.chevyhhr.net/forums/how-...-system-60614/


P0172 indicates low fuel pressure, air leak in exhaust before the first catalytic converter, usually in the flex pipe.
dirty MAF sensor, use the proper MAF sensor spray cleaner


https://www.obd-codes.com/p0172

 

So my thermostat is junk and I need to look over stuff again?

Could it be temp sensor? Most engines have one on the block somewhere.

 

In case it’s the flex pipe

https://www.chevyhhr.net/forums/how-...ex-pipe-31536/