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Discussion Starter #1
I have low MPG around 11.5 MPG combined, done 40000 Miles Only , Air filter new , about to change spark plugs for 1st time next week.
any suggestion e.g. clean the front O2 sensor.
already cleaned MAF and MAP sensors .
 

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Can you post your shift points.
and what is your engine RPMs at 55, 65?
 

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Is this a new thing or has it always been that way? Do you drive in the city a lot or lots of short drives?
 

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Respectfully harry54,
You have done many things including having just changed plugs, which means you are very hands on....
So I apologize if some of my ideas are dopey,
I am inquiring into your diagnostic journey.

My wife drives a 2012 AWD, and she now is getting 16.3 mpg, up from 15.1 about 2 months ago.... I had her intake valves walnut blasted.....at about 79k miles. (And new plugs since we were in there already)
Her average trip is 10 minutes, stop and go driving in the "burbs" with the occasional 45 minute highway blast to go to a shopping mall or visit our kids......

So I concur, your milage is low.


My 2 cents
Are you using top tier gasoline? ( top tier, includes regular gasoline...it does not imply mid grade or premium.) if not, only use only top tier.

Regardless, ^^ , try a few tanks of shell premium, or chevron premium..... it will clean carbon from fuel injectors and clean any carbon build up on upper piston ring. I know it's an extra 80 cents per gallon , and definitely not worth it on an mpg basis, I suggest it for its cleaning of carbon benefits

also before your next oil change, run a tankful of Techron fuel system treatment, it has PEA, and is similar to what GM sells at dealership, and it is good for the plastic parts of your fuel system, will clean fuel injectors and will clean carbon off upper piston ring...
You need to change your engine oil after you do this... piston blow by and the PEA, will contaminate the engine oil....
then make sure you use dexos approved 100% synthetic engine oil.


It should go without saying ... but .. you need to check engine oil levels every 1000 miles, then more often when oil consumption is detected, after all all gdi (gas direct injection) engines will eventually burn oil.

When was the last time you cleaned your throttle body?
I know you were looking at it when you changed your plugs...
Lots of crankcase gunk gets into your air box ( between air filter and throttle body) since the clean side PCV has reverse flow under wide open throttle., which deposits crankcase gunk into airbox.
inspect the air box and clean the crankcase goop, I am sure you did this, since you had to remove intake manifold to change plugs.... was your air box oily?

And by the way, how were your spark plugs?

Did you look at your intake valves ? While you were changing your plugs?

Tire pressure? Make sure your tires are pumped up to 36 psi, don't rely on the cars tire pressure monitor for accuracy, buy the $30 Michelin tire pressure gauge, accurate to 0.1 psi.....

And finally, since you are asking about O2 sensors,
do you have the $70 OBDlink mx+ Bluetooth device that you can pair with your iphone?
You can see o2 sensor voltages as you drive,
fuel trims, engine temperature and other parameters,
that might help find root cause of lower mileage......
In addition to seeing all gm codes, . ,,,,, if any are thrown.

I have one ^^ , if you wanted to know about any specific parameter, to compare your parameter values, I could let you know what I am getting on the 2012 traverse....
 

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Respectfully harry54,
My wife drives a 2012 AWD, and she now is getting 16.3 mpg, up from 15.1 about 2 months ago.... I had her intake valves walnut blasted.....at about 79k miles. (And new plugs since we were in there already)
Not trying to totally derail this thread as this could be relevant... how much was the walnut blasting? It's one of those mysterious things that noone seems to post the price paid.
 

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Walnut blasting of all 6 intake valves,
including a new intake manifold gasket ($20) was $470, in the western / southwest burbs of Chicago.
They also had a free (older) courtesy car......
 

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Discussion Starter #12 (Edited)
Hi Threenox

Changing the spark plugs did not affect MPG , it is still low same. I did not remove intake manifold! me and my son managed to do it without removing it.

Two of the sparked plugs were slightly burned and white powder found on the tip of them, those ones were on the back.
No codes from scanner . but i have the parameters while idling only i can send it to you. i am not really good at analyzing these numbers.
to add even while idling the MPG is lowering fast.
 

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Harry 54,

My 2 cents,
Those spark plugs could be a huge clue. Only 2 of 3 on bank 1 have white powder, not all 3, ....

White plugs usually mean it's running lean, which means it is not getting enough fuel, or getting too much air.
White plugs could mean it is running too hot, which is not good for an engine.

Looking at fuel trims might tell you bank 1 is running lean. Fuel trim should hover at 0%.
Running lean would mean a positive fuel trim, ( say +15%)
that is,
Traverse is adding extra fuel into cylinders trying to get fuel trim to normal 0% where it should be,
traverse is adding extra fuel to bank 1 fuel injectors, so that the engine will not run lean.

Since only 2 cylinders are running lean, it might eliminate the normal cause of engine running lean... (vacuum leaks)
Running lean might mean a head gasket has an issue between those 2 cylinders.

A video on head gasket change on older V6 equinox,


Perhaps you should bring it to your known local friendly mechanic, bring the spark plugs with you.
A compression test might be your next step.....
Who knows?
 

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Discussion Starter #15
Hi

To confuse the matter more , here the values :
Short Term Fuel Trim -Bank 1(%)-0.8
Long Term Fuel Trim - Bank 1(%)-0.8
Short Term Fuel Trim -Bank 2(%)2.3
Long Term Fuel Trim - Bank 2(%)-1.6
------------------------------------------------
Short Term Fuel Trim -Bank 1(%)0.8
Long Term Fuel Trim - Bank 1(%)-0.8
Short Term Fuel Trim -Bank 2(%)3.1
Long Term Fuel Trim - Bank 2(%)-0.8
---------------------------------------------
Short Term Fuel Trim -Bank 1(%)-0.8
Long Term Fuel Trim - Bank 1(%)0.0
Short Term Fuel Trim -Bank 2(%)3.9
Long Term Fuel Trim - Bank 2(%)-0.8
---------------------------------------------
Short Term Fuel Trim -Bank 1(%)3.1
Long Term Fuel Trim - Bank 1(%)0.0
Short Term Fuel Trim -Bank 2(%)-1.6
Long Term Fuel Trim - Bank 2(%)0.8
---------------------------------------------------
 

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Discussion Starter #16
For the MAF :
Air Flow Rate from Mass Air Flow Sensor(g/s)5.69
Absolute Throttle Position(%)15.7
------------------------------------------
Air Flow Rate from Mass Air Flow Sensor(g/s)5.24
Absolute Throttle Position(%)15.7
----------------------------------------------------------------
Air Flow Rate from Mass Air Flow Sensor(g/s)4.71
Absolute Throttle Position(%)18.4
--------------------------------------------------------------
Air Flow Rate from Mass Air Flow Sensor(g/s)4.57
Absolute Throttle Position(%)18.8
---------------------------------------------------------------
 

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Fuel trims look normal,
And
So does mass air flow sensor at idle.

So perhaps spark plugs were not saying running lean....!
 

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There are very few problems that will decrease fuel economy by 40% and you need the help of a true mechanic to troubleshoot the engine. Most mechanics are clueless and depend 100% on the scope to tell them what to fix. OK if it is a check engine light type of problem but not for anything else.

I would expect there to be some level of performance problem like hesitation when engine is cold or when accellerating up a hill or idle fluctuating at a stop. In terms of things to check I would put a sticking caliper(s) or a bad head gasket at the top of the list. A bad head gasket will allow coolant to dilute the fuel and it takes very little to affect performance and it can take another 20K miles to fail to the point where there is significant coolant loss.

I would avoid replacing all the various emissions components on a try, try, and try again to fix the problem. It will be a waste of time and money.

Lastly, the Traverse fuel tank access cannot be used with a locking gas cap or even a latch on the cover. All too easy for someone to syphon off gas for their own use.
 

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So my recent driving has been from home to train station- 6 miles each way- via avenue with many stop lights. MPGs have been 15-17 MPG.
For December- I have been driving into work on the freeway. With it being Los ANgeles, I do get stuck in bumper to bumper- that then opens up then comes to a crawl.
But for these 2 tankfuls, im at 21 MPGs.
 

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I'm just throwing something against the wall here... plugged cat possibly? I've seen a number of threads over the years where a plugged cat wreaked havoc on fuel mileage and driveability.
 
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