2011 mpg terrible

606 Views 18 Replies 7 Participants Last post by rbarrios, 3 d ago

rewtiger

Discussion Starter · 24 d ago

long story short, i have about 136,000 miles on my 2011, recently had some major work done due to check engine light for read cat converter needing replaced. also, prior to this i was getting really bad gas MPG, so we thought while doing the cat converter, looked into the plugs, coil packs, etc. come to find out had more issue then thought. read valve cover was leaking really bad, and oil was getting down in 2 of the rear plug hole.

so we decided to replace the valve cover gaskets and everything needed for that repair, also replaced all the plugs, coils, and gaskets needed for vale covers. plugs were almost gone, so thinking all this was new would help gas MPG, in doing all this, we rest the computer in the car buy holding + & - battery terminals together to clear anything weird going on with computer. so everything fixed, codes cleared correctly, and drives great, but gas MPG is terrible still. my normal driving is rural highway to and from work each day approx 10 miles between 45-55 mph. when you look at the avg mpg on display it will not seem to hold like it did in the past, i was getting approx 18-20 mpg prior to all this repair work. if i really feather things i can get it around 16-17 mpg, but i have always been able to hit the check button on the dash, and get it to hold better. just not sure why it drops so quickly now with better parts then before.

i have read other treads that state something about the deal can run software test or recall, with resetting the computer could i have messed something up? can my regular mechanic do any of these tests or do you have to take to dealer? just trying to get it back to somewhat of normal Gas MPG. i also said that maybe i just need to take a long drive and see if it might fix itself since i'm only driving 10 miles at a time and it can't learn, any help or suggestions would be great.

thanks

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rbarrios

· #2 · 24 d ago

Did you replace the oxygen sensors?
Sounds like you had not reset the mpg parameters in a while. The batt reset cleared the mpg values, and now youre seeing big changes because it has very little data.

Dont reset.... you have many miles of data to get an average... the mpgs change very little.
Reset often, less miles to take average.

I reset my values at every gas fillup.

Reactions: 1

rewtiger

Discussion Starter · #3 · 24 d ago

rbarrios said:
Did you replace the oxygen sensors?
Sounds like you had not reset the mpg parameters in a while. The batt reset cleared the mpg values, and now youre seeing big changes because it has very little data.

Dont reset.... you have many miles of data to get an average... the mpgs change very little.
Reset often, less miles to take average.

I reset my values at every gas fillup.

we did not replace o2 sensors, because nothing stated too do that. i had a feeling with doing the battery clear might mess with things. so you mean the check mark on the dic, don't reset , or do reset, or wait till each fill up? thanks

rbarrios

· #4 · 24 d ago (Edited)

Oxygen sensors get lazy.
That is their response time slows down.
On my now sold 2010, i changed all 4 at 100,000.
No engine light but thats what i do. Also helps to keep the cats from slowly dying faster i think.
I sold my 2010 with 197,000 and still getting 22-24 mpg on my weekly commute to work.

You can reset with checkmark whe ever you want.
I personally do it at every gas tank refill.
I usually refill on sunday, reset, and monday commute starts... by the end of the workweek 22 to 24.
Very good way to monitor performance.
By the way, i bought a 2023 traverse. Same commute, im getting 28 mpg.
Only 3200 miles.
3.6 with 9 speed.... they really hit a home run with that combo.
I mean my 3.6 with 6 speed was great. But very pleasantly surprissed at boost in mpg with the 23.

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rewtiger

Discussion Starter · #5 · 24 d ago

rbarrios said:
Oxygen sensors get lazy.
That is their response time slows down.
On my now sold 2010, i changed all 4 at 100,000.
No engine light but thats what i do. Also helps to keep the cats from slowly dying faster i think.
I sold my 2010 with 197,000 and still getting 22-24 mpg on my weekly commute to work.

You can reset with checkmark whe ever you want.
I personally do it at every gas tank refill.
I usually refill on sunday, reset, and monday commute starts... by the end of the workweek 22 to 24.
Very good way to monitor performance.
By the way, i bought a 2023 traverse. Same commute, im getting 28 mpg.
Only 3200 miles.
3.6 with 9 speed.... they really hit a home run with that combo.
I mean my 3.6 with 6 speed was great. But very pleasantly surprissed at boost in mpg with the 23.

totally get what your saying, i guess with us resetting with the battery cables, it wiped out everything, and now it has to relearn, and could take long tine, correct? bad thing is, with the o2 sensors, there so $$$$$, i used to get like 18-20 mpg on avg, and then more on long trips, as much as 23-25 mpg when we travel south on vacations. so i guess will just give it time, and only reset as you suggested on fill ups, hopefully it gets better. like stated we just replaced the rear cat converter, and all plugs and coils.

that's great about the vehicles you have and what your getting mpg, wish i was getting that. using more gas then i'd like with being is PA gas is 3.79 per gallon. i did try non-ethanol gas on last fill up had a 1/4 of a tank left and it was $70, yikes. thanks for your help and suggestions, will try and be patient, lol

cfedor

· #6 · 24 d ago

Change the coil packs and plugs(gap them properly), the mass air flow sensor, and the air filter. May want to change out the solenoid fuel purge valve that is in the engine compartment. my 08 cxl awd had 2 misfires going on on #1 & #4, was getting 10mpg in town. Changed all of the above mentioned, and now getting 16-18mpg in town.

rbarrios

· #7 · 24 d ago

Rewtiger.... this may make you feel better, 3 weeks ago took a roadtrip.. 3 hrs from home. Gas was $6 for regular at our destination.
The nearest gas station to my house was $4.85 this morning.
I plan my gas fillups to coincide with my costco runs.. $4.39

Reactions: 1

Sparky

· #8 · 16 d ago

rewtiger said:
long story short, i have about 136,000 miles on my 2011, recently had some major work done due to check engine light for read cat converter needing replaced. also, prior to this i was getting really bad gas MPG, so we thought while doing the cat converter, looked into the plugs, coil packs, etc. come to find out had more issue then thought. read valve cover was leaking really bad, and oil was getting down in 2 of the rear plug hole.

so we decided to replace the valve cover gaskets and everything needed for that repair, also replaced all the plugs, coils, and gaskets needed for vale covers. plugs were almost gone, so thinking all this was new would help gas MPG, in doing all this, we rest the computer in the car buy holding + & - battery terminals together to clear anything weird going on with computer. so everything fixed, codes cleared correctly, and drives great, but gas MPG is terrible still. my normal driving is rural highway to and from work each day approx 10 miles between 45-55 mph. when you look at the avg mpg on display it will not seem to hold like it did in the past, i was getting approx 18-20 mpg prior to all this repair work. if i really feather things i can get it around 16-17 mpg, but i have always been able to hit the check button on the dash, and get it to hold better. just not sure why it drops so quickly now with better parts then before.

i have read other treads that state something about the deal can run software test or recall, with resetting the computer could i have messed something up? can my regular mechanic do any of these tests or do you have to take to dealer? just trying to get it back to somewhat of normal Gas MPG. i also said that maybe i just need to take a long drive and see if it might fix itself since i'm only driving 10 miles at a time and it can't learn, any help or suggestions would be great.

thanks

You've probably already checked...but verify there are no fuel leaks.
The ECM should get all the values reset within 100 miles if you have the right driving conditions. Most values set quickly, but Evap System values may require a few cycles of heating and cooling the system. I wouldn't really expect O2 sensors to affect gas mileage very much, but I could be misguided. Gas flow in the fuel injection system is dictated by the mass of the air. MAF (Mass Air Flow) sensor should record 14.7 grams of air for each gram of fuel. The ECM uses the data from the fuel flow and MAF to operate the fuel injectors. The MAF is in the throttle body.
So other questions... air tire pressure, brakes, (Dragging? see if the wheels are getting really hot...) Wheel hub bearing, Wheel alignment. Anything you can think of that might cause rolling resistance.
Also verify your gas mileage using the old method of filling the gas tank, and comparing how much fuel you used for the miles driven. In case it's a fuel flow sensor issue. These are just my thoughts.
I just read some other interesting information where the O2 sensor can indeed be used to change the ration of Air to fuel. Not sure if Buick does this or not, but it seems this is important where the addition of Alcohol and additives in varying ratio's will have an impact on the best air to fuel ratio. Efficiency can be improved by O2 sensor readings

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electbc

· #9 · 16 d ago

My suggestion is get yourself a Bluetooth OBDT2 reader so you can monitor the vehicles vital signs especially O2 sensor cat temps. I am suspecting an injector was sticking and caused raw fuel into the cat, still may be sticking. Try a couple bottles of Techron on the next 3 fillups if nothing else. You do use Top Tier Fuel don't you?

wither 5

· #10 · 15 d ago

I don't know about rewtiger, but rbarrios made my day when he said gas prices at his destination are $6 gal. I live in Ohio and they're only about $3.35.

electbc

· #11 · 15 d ago

Oh BTW Rbarrios. is you new ride FWD or AWD? I know my Buick Dealer sends me ads for a new Enclave where I can save $300 a year on gasoline over my 2015. I am hoping to get another 100k out of this one.

SamUnfiltered

· #12 · 4 d ago

I get 13.8 mpg on my 2012 Enclave

rewtiger

Discussion Starter · #13 · 3 d ago

rbarrios said:
Rewtiger.... this may make you feel better, 3 weeks ago took a roadtrip.. 3 hrs from home. Gas was $6 for regular at our destination.
The nearest gas station to my house was $4.85 this morning.
I plan my gas fillups to coincide with my costco runs.. $4.39

good lord, that is nuts on the gas prices, just total bs what we are all paying right now, no need for it.

BTW, on conclusion on the MPG issues, still not doing the best at the gas mileage, i have only been trying to hit the reset check mark at gas fill ups, sometimes still down at the 15-16 MPG. just not holding for some reason. you stated before about re-settting often? i think my issue is this, i don't have a long enough commute for it to hold, i can reset it, use the cruise, and its better, but as soon as i have to climb a hilly raid, it drops like a stone for some reason. guess i have to keep doing the check mark reset, correct? told my wife just need to take a long drive and see.

rewtiger

Discussion Starter · #14 · 3 d ago

SamUnfiltered said:
I get 13.8 mpg on my 2012 Enclave

wow, that's not good at all, how many miles, and have you replaced any of the main elements, like spark plugs, coils, as others havs suggested, o2 sensors, etc? that's not good at all

rewtiger

Discussion Starter · #15 · 3 d ago

electbc said:
My suggestion is get yourself a Bluetooth OBDT2 reader so you can monitor the vehicles vital signs especially O2 sensor cat temps. I am suspecting an injector was sticking and caused raw fuel into the cat, still may be sticking. Try a couple bottles of Techron on the next 3 fillups if nothing else. You do use Top Tier Fuel don't you?

i do have one, guess i will have to hook up and check things out more, just thought with doing all the repairs, plugs, coils, and cat and resetting the computer it would have gotten better.

rewtiger

Discussion Starter · #16 · 3 d ago

Sparky said:
You've probably already checked...but verify there are no fuel leaks.
The ECM should get all the values reset within 100 miles if you have the right driving conditions. Most values set quickly, but Evap System values may require a few cycles of heating and cooling the system. I wouldn't really expect O2 sensors to affect gas mileage very much, but I could be misguided. Gas flow in the fuel injection system is dictated by the mass of the air. MAF (Mass Air Flow) sensor should record 14.7 grams of air for each gram of fuel. The ECM uses the data from the fuel flow and MAF to operate the fuel injectors. The MAF is in the throttle body.
So other questions... air tire pressure, brakes, (Dragging? see if the wheels are getting really hot...) Wheel hub bearing, Wheel alignment. Anything you can think of that might cause rolling resistance.
Also verify your gas mileage using the old method of filling the gas tank, and comparing how much fuel you used for the miles driven. In case it's a fuel flow sensor issue. These are just my thoughts.
I just read some other interesting information where the O2 sensor can indeed be used to change the ration of Air to fuel. Not sure if Buick does this or not, but it seems this is important where the addition of Alcohol and additives in varying ratio's will have an impact on the best air to fuel ratio. Efficiency can be improved by O2 sensor readings

i do not have any fuel leaks, and don't feel anything is dragging to make it slow down for it to use more fuel. as stated i can hit the check mark button on the dash to reset things, and depending on driving conditions, hills and such i can get it to hold like 23-25 mpg, but as soon as i hit a hill it drops like a stone, nothing holds at all. its so weird. i guess i can see if my garage buddy can check the MAF with his computer equit for me, see what is going on. he does suggest i run like a seafoam thru the fuel system, one in a while too. i did do the old school figuring for the gas MPG and got approx the same as it was showing like 16-17 MPG. really appreciate your help and advice, will see what my garage says about your info. thanks

SamUnfiltered

· #17 · 3 d ago

rewtiger said:
wow, that's not good at all, how many miles, and have you replaced any of the main elements, like spark plugs, coils, as others havs suggested, o2 sensors, etc? that's not good at all

155,629 miles. I have not replaced anything. Except the Catalytic Converter.

rbarrios

· #18 · 3 d ago

Electbc, sorry had not seen your question.
Its,FWD.
My 2010 gave me 22 to 24 mpg on weekly commute.
My 2023 is getting 28-30 mpg
The onstar app is showing 27 mpg lifetime.(4,590 miles)
So recently got this... staying in the slow lane.... then i hit a 20 mile backup.... i ended up at 27 or so mpg after 280 miles roundtrip.

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rbarrios

· #19 · 3 d ago

Electbc...funny you mention the savings...

2 days ago gave my kids a math problem to calculate :
Wording was elaborate... like youd see on some exam.
In short.
With weekly total mileage commute of 300 miles and $4.39 / gal of gas and 22 mpg vs 28 mpg.
1)gas usage of the 10 vs 23
2) the difference in gas use
3) the savings in $.

Glad to say they both got it right.
2023 uses 2.9 gal less ($12.73 )
$662 less in gas for my daily commute over a year.

Sorry to the op for going off topic

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