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Discussion Starter · #1 ·
I have a 2017 Chevy Traverse. A while back my mass air flow sensor had went out. I didn't know it was the mass air flow sensor right away, it just lit up the check engine light and started not wanting to accelerate and seemed like the engine was choking. I started with the air filter, replaced that, then I went and had it plugged in to the reader and it came back my purge valve was no good, replaced that, still had the same issue, just kept getting worse. Went and plugged it back in again and results were bank 1 was running to rich. I wasn't really sure at that point so I started watching videos and stumbled across one that said it could be the Mass Air Flow Sensor, replaced that, and fixed the issue right away. Before this all happened I would average a out 17.3 mpg but during the time spent figuring out what was going on the mpg had dropped to around 5 or 6 mpg. After replacing the sensor it jumped back up to 12 mpg but never any more then that. Now, about 3 months later I'm getting 9 mpg. I've checked my air filter multiple times as well as the housing and intake tube, and replaced my spark plugs. What can I do to fix this issue. No check engine light is on and the rig seems to run just fine other then the mileage.
 

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I started losing mpg on my Tahoe around 70k miles. Changed plugs first then the O2 sensors at 80k miles and got back 2-3 mpg with the O2 sensor change. That's a big deal on something that only gets 18-19 mpg then drops to 15 mpg. O2 sensors read fine on scan tool and did not set any codes either and it ran and towed like a champ. AC sensors only if you go that route. Hopefully you used a AC Delco MAF, aftermarket sensors are garbage.
From now on my fleet is getting it's plug and O2 sensor changes at 80k miles.
 

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Discussion Starter · #3 ·
So you think I should change out the O2 sensors?? If so I start with the closest to the front of the car right?? Or do I just change them all at once?? Also no I didn't use AC Delco, I can't remember the brand off hand. Should I change it out again and put the AC Delco MAF in??
 

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So you think I should change out the O2 sensors?? If so I start with the closest to the front of the car right?? Or do I just change them all at once?? Also no I didn't use AC Delco, I can't remember the brand off hand. Should I change it out again and put the AC Delco MAF in??
I'd put the AC MAF in first and see how it runs. Rock Auto is my go to for AC parts, box store junk only if I'm stuck for a temporary fix.
If your miles are up there then the O2 sensors next if mileage doesn't improve, the one's closest to the engine are the ones that control fuel mixtures. O2 sensors get ''lazy'' over time, how many times I've seen people post up pictures of sensors with it's end ''cage'' melted off and sensor was still not coding out.
 

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How are you determining your MPGs?
via the DIC numbers or hand calculate?

But I would do as repairman54 says.
 

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just to make sure, do you reset the parameters when you refill the tank?
 

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at 100,000- I replaced all 4 of my O2 sensors.
I was NOT having any issues.
At 100K I did a bunch of maintenance. (plugs, oil, filters, struts, brakes, O2 sensors).
My Traverse continues to give great mileage.
Im about to hit 161,000.
This week with driving on the freeway- 55-60, this tankful is giving me 22-23 MPG DIC.
 
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Discussion Starter · #10 ·
Yes I've reset it pretty much as often as I can actually. Fill up, cleaning filter, checking vacuume lines, etc.......
 

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Discussion Starter · #12 ·
I started losing mpg on my Tahoe around 70k miles. Changed plugs first then the O2 sensors at 80k miles and got back 2-3 mpg with the O2 sensor change. That's a big deal on something that only gets 18-19 mpg then drops to 15 mpg. O2 sensors read fine on scan tool and did not set any codes either and it ran and towed like a champ. AC sensors only if you go that route. Hopefully you used a AC Delco MAF, aftermarket sensors are garbage.
From now on my fleet is getting it's plug and O2 sensor changes at 80k miles.
I know you recommended the AC Delco but I have a question, what's your take on duralast MAF sensor??
 

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I know you recommended the AC Delco but I have a question, what's your take on duralast MAF sensor??
When it comes to sensors it's factory parts only on vehicles. My exception is only if I need it to get to work then it gets replaced with OEM parts. Too many weird issues with aftermarket or the not lasting as long as OEM parts. Rock Auto has GM one for $51.00 . I had a Duracrap ignition coil on a old Blazer give me fits, was erratically leaking spark out it's side causing erratic misfires right out of the box new just like the one I was replacing. Lifetime guarantee means of lifetime of replacing them, not for me.
 

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speaking of lifetime guarantee....
At 161,000- I still have the factory rear brake pads. maybe 20-30% left. The wear indicator still not close to the rotor.
Early models came with Akebono brake pads. Really nice pads. Low dust.
I could get some auto part pads with lifetime warranty for $20-$30...
Since Im about to flush the brake lines (I last flushed 5 yrs ago).... I ordered Akebono rear brake pads. I figure theyll last another 160,000 miles.
$45 on rock auto, with tax and delivery- $55. dont want to mess with the cheapies.
The pads should be delivered today.
I also bought the AC DELCO brake fluid that helps quiet the brake pedal squeek.
I did this 5 yrs ago- and it did quiet the noise. Eventually it returned. The part # for the ACDELCO fluid has been updated. Pep Boys actually had it in store.
 

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All good advice. I'd also recommend fuel system cleaner as dirty injectors with a bad spray pattern could cause rich condition. Being direct injection, if the intake valves are gummed up that can cause fuel mileage issues too
 

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Discussion Starter · #16 ·
When it comes to sensors it's factory parts only on vehicles. My exception is only if I need it to get to work then it gets replaced with OEM parts. Too many weird issues with aftermarket or the not lasting as long as OEM parts. Rock Auto has GM one for $51.00 . I had a Duracrap ignition coil on a old Blazer give me fits, was erratically leaking spark out it's side causing erratic misfires right out of the box new just like the one I was replacing. Lifetime guarantee means of lifetime of replacing them, not for me.
Hey, I know it's been awhile but just wanted to see if you had anymore ideas about my fuel mileage?? I replaced the MAFS again with new AC Delco, also I've replaced all 6 plugs, air cleaner, and tried some additives/system cleaner. Replaced purge valve as well. Vehicle on a good day says I'm averaging between 10 to 12 miles per gallon max, and that's really only if I really baby it and try and cheat it with absolutely no heavy acceleration and coasting whenever possible. I've also calculated that MPG manualy and came up with the same MPG. Any thing else you can think of?? Thanks again and in advance for your time.
 

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Hey, I know it's been awhile but just wanted to see if you had anymore ideas about my fuel mileage?? I replaced the MAFS again with new AC Delco, also I've replaced all 6 plugs, air cleaner, and tried some additives/system cleaner. Replaced purge valve as well. Vehicle on a good day says I'm averaging between 10 to 12 miles per gallon max, and that's really only if I really baby it and try and cheat it with absolutely no heavy acceleration and coasting whenever possible. I've also calculated that MPG manualy and came up with the same MPG. Any thing else you can think of?? Thanks again and in advance for your time.
Try the last post (#87) in this thread:

 

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Hey, I know it's been awhile but just wanted to see if you had anymore ideas about my fuel mileage?? I replaced the MAFS again with new AC Delco, also I've replaced all 6 plugs, air cleaner, and tried some additives/system cleaner. Replaced purge valve as well. Vehicle on a good day says I'm averaging between 10 to 12 miles per gallon max, and that's really only if I really baby it and try and cheat it with absolutely no heavy acceleration and coasting whenever possible. I've also calculated that MPG manualy and came up with the same MPG. Any thing else you can think of?? Thanks again and in advance for your time.
Did you ever sort this out? I've been noticing my 12's mileage has dropped off significantly and the wife is only averaging 12-13 these days. We used to get around 17-18. The intake valves are clean (walnut blasted them at 100K) at 125K now, spark plugs changed at 90K, 02's changed out 10K ago and car runs smooth with no issues or CEL's. I'm going to replace the intake gasket (as I left the original one in there when I blasted the valves), clean the TB and also replace the MAF sensor as they are pretty cheap ($50 for AC Delco OEM). I'll see how she responds, but not sure if I should go ahead and replace the coils or not as I'm on the original coils, but don't know if they could be getting weak and causing bad mileage?

Plus if I go with the coils, I'm thinking of the Delphi's as you can get them for $34 a piece on amazon, vs $55+ for the OEM Denso's and the Delphi's have great reviews and are a quality coil. Anyone have a personal experience with the Delphi's?
 

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how about dragging brakes?
Coils... I personally would stay with OEM. the 09s had Bosch, my 2010 Denso. Delphis? I have no input on those.
Im at 164,000 and still on the factory coils.
Recently replaced the factory rear brakes with Akebono... but the factory stainless steel brackets had some buildup on them... so yours may not be allowing the brake pads to smoothly move back and forth easily.
You say youre going to replace the MAF sensor- but have you ever cleaned it?
In city I can get lows of 15-17 lately.
not much use of the AC.
About 1 month ago- I gassed up and hit the highway- headed towards San Diego.
Then I ran into an accident/backup that delayed me for a while.
But I had been going at an easy 55 till the backup.... this is the highest... then it went downhill from being stuck in traffic- stop and go.

Have you recently gassed up and hit the highway for a drive where youre in 6th gear... easily cruising along in the right lane? Engine purring along at 1500 rpms?
It would be interesting to see what your vehicle registers. Is your vehicle going into 5th and 6th?

 

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how about dragging brakes?
Coils... I personally would stay with OEM. the 09s had Bosch, my 2010 Denso. Delphis? I have no input on those.
Im at 164,000 and still on the factory coils.
Recently replaced the factory rear brakes with Akebono... but the factory stainless steel brackets had some buildup on them... so yours may not be allowing the brake pads to smoothly move back and forth easily.
You say youre going to replace the MAF sensor- but have you ever cleaned it?
In city I can get lows of 15-17 lately.
not much use of the AC.
About 1 month ago- I gassed up and hit the highway- headed towards San Diego.
Then I ran into an accident/backup that delayed me for a while.
But I had been going at an easy 55 till the backup.... this is the highest... then it went downhill from being stuck in traffic- stop and go.

Have you recently gassed up and hit the highway for a drive where youre in 6th gear... easily cruising along in the right lane? Engine purring along at 1500 rpms?
It would be interesting to see what your vehicle registers. Is your vehicle going into 5th and 6th?

Brakes don't seem to be an issue as I just put new rotors and pads on her 9K miles ago and all the calipers checked out as well as cleaned and re-greased the slide pins. Used the AC Delco rotors all around and Akebono pads as well. Don't see any change in deceleration when letting off or pulling side to side and no excessive brake dust on any one wheel. I've cleaned the MAF and actually just cleaned it about 2K ago when I pulled the intake boot and cleaned the oil out as well. As to the fill-up and highway mileage, we just took a trip to Beaumont (about 2 hours away) from Houston for my nephews graduation last week and the best I could muster with 70-75 average speed and flat highway (no hills) with no traffic and easy acceleration (keeping RPMs down) was 18-18.5 for the whole trip. I used to be able to get 20-22 with no problem. Trans shifts fine and tires are brand new (properly inflated as well) - was getting same reduction in MPG with the older tires so that's not the difference here. Kind of stumped as there is no codes and car idles, starts and runs fine, just MPG has dropped? I figured MAF is a good start as it directly controls the Fuel Trims and for $50 is not a bad diagnostic tool and I don't feel bad for throwing parts at it as it can't hurt to have a new OEM MAF on a car with 125K Miles anyway. If MAF and Intake Gasket don't help, I'll throw some new coils at it and if nothing changes, I'm stopping there and just living with the slightly reduced MPG as the car is not worth throwing more and more parts at it without knowing for sure.
 
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