Running Rich
 

Hello Im new to all of this so if i'm doing something wrong let me know.

I have a 2009 hhr LS 110,000 miles it has the 2.2 and its getting the 0172 code. It had hard starts and ran sluggish. The first thing I did was replace the MAF sensor and put in a new air filter. No change.

The next thing I did was a fuel pressure test. It got 60lbs with key on engine off. My Haynes book says thats within spec. It puts out 64lbs with the engine running (I havent found a spec with engine running).

I did a leak down test and the gauge did not move for 5 minutes. I am assuming the fuel pump, regulator and injectors are ok?

The next thing I did was replace the upstream 02 sensor and did the plugs (they were due anyway). The hard starts are gone and it doesn't run sluggish all the time. I am gettin decent mileage. I have reset the light a few times and it always come back on. Thought it might be bad gas so I took it on a 300 mile trip. 3rd tank of gas and the light is still on.

The only other thing I can think of is about 2500 miles ago I let Valvoline do a flush on my coolant system (Dumb).....well somehow they messed up the pet**** gasket and it got hot. Ive heard the thermostat can cause the 0172 code too. It seems to run cooler than it used to. On my trip it never got hotter than about 195 degrees on a 85 degree day. it used to run somewhere around 200 degrees. I thought about replacing the thermostat but a 180 degree thermostat is standard. I replaced all the parts with AC Delco.

I am stuck any help is appreciated. Thanks

https://www.yourmechanic.com/article...-blake-griffin

Check for vacuum leaks. How is the air filter. How is the engine temp sensor. Look at the flex pipe. The EVAP purge valve could be faulty.

The O2 sensor is last on the list
There is only a O-ring on the radiator drain.
Should run about 190F, 195F is a bit high.

Thanks Donbrew.
I forgot to mention I did check the flex pipe and there were no leaks. The air filter is brand new. Ill check for vacuum leaks tomorrow as well as the evap and temp sensor.
Thanks

Injectors, MAP, or Flex pipe.

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

I'd inspect the wiring harness to the MAF, and reinspect the flex pipe

Hey guys thanks for all the help. I replaced the Evap purge valve and tested for vacuum leaks reinspected the flex pipe again and no luck it still set the code. I finally broke down and took it to the local garage and he said the computer was registering too high alcohol content (65%) he reset it. I'll see if it sets the code this weekend. I don't understand how this can happen to a flex fuel vehicle. According to the bulletin the guy gets this is starting to be a common thing. If anyone can explain it to me I'd appreciate it. Thanks again for all your input.

Too high alcohol = too much oxygen in the exhaust.

The computer calculates the alcohol from oxygen content from the O2 sensors. The more O the more alcohol.

Explained in 2 sentences! Maybe your mechanic should do some reading?

This search I did https://www.chevyhhr.net/forums/sear...&query=alcohol

Shows at least one instance that the problem was a timing chain not bad enough to cause a P0016 yet. You might take the cam cover off and see if there is any slack in the chain.

Thanks,

Yes thanks, The mechanic and I both understand how an 02 sensor works. I was more looking for a explanation of why it was getting the wrong reading especially since its a car designed to burn both types of fuel. The timing chain would be more of the explanation I was looking for.

Thanks

Read the explanation again. Evidently you don't understand as well as you think.

The sensors sense O, the more O the more alcohol is calculated. Introduce more O into the combustion gasses and the O2 sensors calculate more alcohol. The computer reports a higher alcohol content. The computer tries to adjust the A/F based on faulty data.

O can be introduced in several ways, including a cracked flex pipe, a vac leak, an intake valve acting funny.

The timing chain explanation is the same as the O=alcohol.

The computer doesn't know the difference between O in the air and O in alcohol; it assumes O means alcohol.