My daughter's 2011 HHR LT with 2.2L engine has a problem.

When you go to start it after it has been sitting, it acts as a flooded engine. You have to hold the pedal to the floor and crank for a few seconds, and then it runs rough for a few more seconds, and then its ok. It runs perfectly fine after starting it. it does set a P0172 code (System too rich bank 1).

It sounds to me like a leaky fuel injector. I can't think of anything else that would cause this issue. I was planning on getting 4 new injectors from Rock Auto to see if it fixes the issue.

What do you think? Am I missing something else that it could be?

Thanks
Steve

 

A dirty MAF sensor, cracked exhaust manifold or flex pipe can cause the code so could a fuel pressure problem

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

 

The big issue here is the flooded startup condition.

It seems like one (or more) injectors are leaking fuel into the combustion chamber and fuel is accumulating in the cylinder after shutdown (until fuel pressure drops from the leak).

I could look at the fuel pressure after shutdown and see if it drops quickly, though I don't have a reference for how long a good fuel system will hold pressure after shutdown.

Steve

 

Classic.

Do not buy anything or make any changes before you check the stored ethanol % with a scan tool.

What you may find is an erroneously high value. This makes the car start with an excessively rich mix. Then when the O2 sensor gets warm enough (doesn’t take long) it goes to closed loop and LT trim corrects the condition. P0172 means the ECM thinks this correction is excessive, which of course is correct.

From your prior posts I’m pretty sure you will have no trouble doing the ethanol % check, but for future readers, many inexpensive scanners can read this value, but it’s often buried in an unexpected place in the menu. I know the free Torque app will do it.

CLEARING CODES WITH NOT CORRECT, CLEAR, OR ZERO THIS VALUE. (Should be obvious, as it’s not an OBD code, but from prior discussions, it needs to be mentioned.

This is a known issue with GM FlexFuel cars, but I haven’t seen a good explanation from GM. The fix is pretty easy.

Just want to get this out. Will comment further. I have covered this in comments in several prior threads, but have trouble finding them sometimes.

 

The erroneous stored ethanol% problem is known to GM FlexFuels and there is at least one TSB. This issue even affected FlexFuel Silverados built years after they stopped making HHR. Again, I have seen no good explanation of the cause.

Common Common threads seem to be:​​​​​

• Onset of cold weather
• Frequent very short trips
• Failing to shut the car off when refueling

(There are more.)

The definitive diagnosis is to compare the stored ethanol value with the % in a sample from the car. I do not recommend skipping the sampling, but if you find a high stored value and you think there’s regular in the tank, that’s a less definitive but very likely answer.

The quickest fix is to use a capable scan tool to zero the ethanol%.

There is no ethanol sensor in these cars. Instead, the ECM detects a refueling event and calculates a % from sensor data. (This detection includes noting a significant increase in fuel level for sure, maybe 3 gallons or so, maybe a shutdown and restart, IDK for sure. But shut down when refueling, and avoid adding just a gallon or two of different fuel, I.e., a switch to or from E85.)

AVOIDING E85 WILL NOT AVOID THIS PROBLEM. USE OF E85 IS NOT THE CAUSE. (E85 is great stuff for cars that are designed for it, but that’s another subject, so please don’t engage on the merits or hazards of E85 here.)

Based upon my personal experience, with (properly executed) refueling, the car might correct itself. It may do so incompletely and gradually. Another tactic, IF you know both the stored and actual sampled %, is to guesstimate a blend with some E85 to get to two value close to equal.

BTW, it has been postulated that a weak battery can cause ECM hiccups that may cause this.

 

You should put this in the how-to tutorial forum. Then you could just link to it when you need to.

 

Good idea on the ethanol percentage.

We never use anything but regular gas, which is 10% ethanol here. Never used E85.

I have a Bluedriver scanner which reads all sorts of things and does real-time monitoring of parameters with bluetooth connection to smartphone.

I'll check the ethanol percentage tonight when she gets home from work.

BTW, when this started a few weeks ago it also gave a code for a bad oxygen sensor. I replaced the oxygen sensor since it had very high mileage on it (160K+ miles). The code now is only for the rich mixture, no more code for O2 sensor.

It has turned much colder here in the last few weeks, and my daughter has a new job which requires much less driving and shorter trips so those two fit two of your common threads that cause this problem.

Steve

 

Yeah, I actually feel guilty for not doing that yet.

 

I'm wondering if the O2 sensor being bad caused this. The computer might have seen the bad O2 readings and recalibrated the Ethanol % because the O2 sensor reading is also used to calculate the Ethanol %.

I'm anxious to see what the Ethanol% shows tonight. Hopefully I can read it with my Bluedriver scanner.

Steve

 

I’m assuming you saw my all-bold note in comment #5 that using E85 is not the cause of the problem. (I don’t think. But as mentioned, it can be part of the cure.)

I forgot to mention my suspicion that faulty O2 data could be involved. Many warning here to use NTK or GM O2 sensors, and not Bosch.