Doesn't it say "ALCH PCT: 16.9%" ?

 

P0172 is a test for "Fuel Trim System Rich".
P0171 is a test for "Fuel Trim System Lean".

 

Seriously, I'm here asking for genuine help, not to be belittled. I'm not ignoring anyone's advice, if this is the problem, do I need to take it to a garage to get this issue resolved? You may be right, this one's got me fooled, but I am by no means a Master mechanic, but I do believe I'm no dummy either. Yes, the car takes short trips, I'm the only driver now and I always turn my vehicle off when refueling. Yes, I have run E85 a couple times, but mostly run straight gasoline. My reader did show ALCH PCT at 16.9%, if there is some magic reset, that's above my pay grade and my equipment's capability. Appreciate your thoughts and inputs, this is a project car and I'm just trying to get it mechanically sound on my own, I plan on taking it to a professional shop if I can't resolve this here, I'm not in no rush, THANKS!

 

Easy now, we are trying to help. Perhaps a few tanks of fuel with fuel injector cleaner will help.

Did you recheck the scanner readings, see if ALCH percentage has changed.
I don’t believe you’re gonna need a shop to reset anything

 

Ah, so it does! I missed that. I was worried it was higher than that.

My use of the word "ignore" was indelicate. Your indirect answer was buried in a lot of other stuff. Sorry I missed it. Reel in the long toes, no intent to step on them. Appreciate the answers to my other questions. No thanks required for the absurd amount of time I'm devoting to this.

So now, is that that consistent with what it's been fed,lately? "Regular" around here is 10% ethanol. In any event, I wouldn't think that's high enough to cause cause P0172, even if it got zero % ethanol at the pump. But IDK.

E85 is not a bad thing, and avoiding it won't prevent this issue (if that's what it is.)

There is a TSB on this problem. The fix they recommend is resetting the stored ethanol % to zero. It takes a high-capability scan tool to do it. I don't know if it's possible to set it to a specific value. I had a stored 50% but a fuel sample tested 11%. I had the dealer reset it to zero. Didn't charge me much. Took care of it.

They wouldn't have had a clue what to do on their own. Do not assume even a dealer will figure this out for you, much less Joe's garage.

I read one story about this, car fixed itself gradually. Makes no sense to me why it would do it incrementally unless there was O2 sensor trouble.

Do I correctly understand the trouble started after the O2 sensor replacement? Why the replacement? Does the smoke, etc., abate after warmup? Which O2 sensor(s) replaced? Brand/part number? Any other seemingly unrelated codes? (Sorry if already mentioned, running out of energy to go back and look.)

 

I just want you to know that I am truly thankful and appreciative of your time and effort here, I do believe you are on the right track, the symptoms started after I ran a tank of E85 and switched back to 10%, 91 octane fuel. I went ahead and changed out the upstream O2 because the P0053 code had been on for awhile and after checking connector, cleaning sensor, etc., it still showed P0053 code, I never checked wiring, probably should have, but since the sensors are reasonably priced and this one was 16 years old I figured couldn't hurt to be replaced! FYI, before this happened, I did replace the MAF sensor, because it flagged a code. After this didn't fix the issue I was having and the downstream sensor was reading .745V. steady not .45V I went ahead and changed out the downstream sensor and CAT, figured since I planned on keeping this car for awhile, it was money well spent. I put about 4 miles on it the other day and it ran and accelerated fine and no black smoke, but I did seem to notice a rich running odor, I'm just going to keep my fingers crossed and if it comes back, I will probably take it to someone with a multifunction code reader who can reset my ALCH PCT setting, REGARDS.

 

TRIM is not the same as MIXTURE. Trim is the amount of adjustment made to get the mixture to 14.7:1,
The second O2 sensor just monitors the "heath" of the cat. The #1 O2 sensor monitors the mixture. As long as the #2 sensor reads steady and not throwing P0420 you are fine; I found that the internet wisdom regarding the readings are not correct for HHR.
Spending money on a new cat for no reason is not good reasoning. The factory cat will last forever, replacements are not made the same.

The most common reason for P0172 is a vacuum leak that admits unmetered air into the system. The alcohol thing is pretty rare.
Is the P0053 still current? That is for a bad #1 O2 sensor heater. It could cause the P0172.

 

The problem with GM FlexFuels getting confused about ethanol % in the tank is rare but known, even if hardly anyone ever heard of it, and there is a TSB. Not confined to Ecotec.

The following conditions might be found in a case of this problem:

• Onset of cold weather
• Fuel or evap line leaks
• Switching to or from E85, ESPECIALY when failing to turn off when fueling
• Frequent short trips, especially exclusively short trips
• O2 sensor issue
• Slow warmup due to faulty thermostat

The TSB diagnosis is confirmed when the stored ethanol content is significantly higher than the actual sampled content. The TSB prescribes using a scan tool to reset the stored ethanol % to zero. If I could I would instead set it to the actual sampled %, but IDK if that's possible.

The ECU uses 02 sensor data to calculate the %. The O2 sensor doesn't work until the car warms up a bit. The car knows to recalculate the % when it senses you've added a certain amount of fuel, and failing to shut down may interfere with that process. So might a cold engine.


I would:

1. Fix the O2 sensor problems, especially #1. No Bosch O2 sensors. NGK.
2. Make sure the car warms up quickly, and if not, replace the thermostat that's probably stuck open
3. Fill E0 or E10 91 octane or better, then reset the the stored ethanol % to zero
4. Make sure no one leaves the car running when fueling
5. If frequent short trips are required, take a longer drive once in awhile

Disconnecting the battery will clear OBD-II codes, but will NOT reset the stored ethanol %.

Your car may have begun to correct itself on its own. If it still smells rich to you be very very sure you're not smelling a fuel leak.

E85 is good stuff. Avoiding will NOT ensure that this problem won't happen. But I would avoid switching back and forth for awhile.

 

The car has been running fine so far, still have a check engine light, will run the OBD scan today and publish results, thanks for all the inputs, hope you all have a great Sunday.

 

Looking forward to the results of the scan. The present ethanol % would be especially interesting. If it's 10% or less like it should be if you're using E10, and you're still getting a code, I would try to hunt down air leaks like Donbrew suggested.