Getting 8.5 mpg need help

[BlueCollarTahoe]

Ok, let's go back to the tires. Are they P-Metrics or LT tires on their now? If LT and you're running the air pressure the same as door sticker you're under-inflated (unless your door sticker is for an LT tire, not a P-Metric).

Did you run those little bottles of Super-Tech yet?

If all else is well I'd start eyeballing those cats. Changed mine and my mileage is finally back up to near where it was when I bought it and getting better. Haven't been driving it lately due to back pain though so no updates on its mpg journey.

AT terrains and the pressure was around 42 i think when i checked it. i ran BGK44 and that Berrymans stuff. how do i check the cats? the temp of the pipes before and after the cat after driving?

 

[swathdiver]

42 psi is a little low but should not be the mpg culprit. 42 psi will support 4,300 pounds an axle (assuming 265-70-17 tire). Your maximum axle weight is probably just under this.

How did the fuel system cleaners work out? As for the cats, that seems like a good way to do it. Maybe someone else will have better ways?

How have the LTFTs been? Last time the right bank was a little off.

 

[Scottydoggs]

im still getting 9 mpg all local stop and go BS driving. im tuned with a wideband. so im fairly certain all my junk is up to *****.

so being a city driver, it just might be normal.

if i get on the hwy for along trip and reset the mpg avg ill hit 20's. but once im back to local its falls back to that 9-10 mpg no matter how much i baby it and feather the gas pedal.

if the cats were really on the way out the truck would have a pretty noticeable power loss, show misfires and even flash the cel when wot.

temp laser can show the cats temp, pre and post cat. when really clogged up you can drive it somewhat hard at night, then look under the truck to see if the cats or pipes are glowing red. if glowing, they are clogged up for sure, but by that time you already feel the power loss. kinda like the old bananas in the tail pipe bit from Beverly hills cop.

 

[swathdiver]

if the cats were really on the way out the truck would have a pretty noticeable power loss, show misfires and even flash the cel when wot.

Mine didn't.

But you're right about the stop and go city driving. Some days I don't even get up to 45 mph and stop at every darn light from home to my destination. And such trips for me like that are often under 10 miles. Even knocks the Montana down to the 16s.

 

[Scottydoggs]

my drive to work is like maybe 5 miles. im right on the hwy for about a mile or so, so i get up to 70 mph and take the next exit lol, then stop and go. stop sign every 500 feet. then the way home is all local roads with a hill on a 45º angle.

looking up it. i know this hill is killing my mpg.

https://www.google.com/maps/@40.877...4!1sQ-bMkZXkEhdwZDozWTm3cA!2e0!7i13312!8i6656

looking down the hill. i went up this after a 6 inch snow storm un plowed. you dont want to go down it even after its been plowed. and you really dont want to fail on the way up either. as tom pettys says, coming down is the hardest part lol

https://www.google.com/maps/@40.878...4!1sHreeqKcg0R0NvMJLYvGT2g!2e0!7i13312!8i6656

 

[BlueCollarTahoe]

42 psi is a little low but should not be the mpg culprit. 42 psi will support 4,300 pounds an axle (assuming 265-70-17 tire). Your maximum axle weight is probably just under this.

How did the fuel system cleaners work out? As for the cats, that seems like a good way to do it. Maybe someone else will have better ways?

How have the LTFTs been? Last time the right bank was a little off.

i didnt see any difference in the mpg after the cleaners. the rb was off at idle? how should i check them or track them? idle, driving at different speeds etc??

im still getting 9 mpg all local stop and go BS driving. im tuned with a wideband. so im fairly certain all my junk is up to *****.

so being a city driver, it just might be normal.

if i get on the hwy for along trip and reset the mpg avg ill hit 20's. but once im back to local its falls back to that 9-10 mpg no matter how much i baby it and feather the gas pedal.

if the cats were really on the way out the truck would have a pretty noticeable power loss, show misfires and even flash the cel when wot.

temp laser can show the cats temp, pre and post cat. when really clogged up you can drive it somewhat hard at night, then look under the truck to see if the cats or pipes are glowing red. if glowing, they are clogged up for sure, but by that time you already feel the power loss. kinda like the old bananas in the tail pipe bit from Beverly hills cop.

no power loss ive heard that from others who had cats go out. i have the AT, a big 50lb push bar and a 25 lb speaker on the front end so may be the difference down to 8.5

Mine didn't.

But you're right about the stop and go city driving. Some days I don't even get up to 45 mph and stop at every darn light from home to my destination. And such trips for me like that are often under 10 miles. Even knocks the Montana down to the 16s.

yea on the highway mine is good its the stop and go when it goes down.

 

[swathdiver]

Compared to your left bank of cylinders, the right was further away from ideal. Just take another reading like you did last time.

I had no perceptible power loss, no flashing CELs, no misfires, etc. when my cats started throwing codes. When we took off the right one, we could see it was falling apart. My mileage has been steadily improving since.

 

[Idaho45guy]

When I bought my Yukon, the average MPG was at 7.6.

It was test driven only around town, apparently. And hard... After driving it a few hundred miles around town, to work and back, and on a trip to the woods, it is showing 17.7 mpg..

 

[bottomline2000]

Compared to your left bank of cylinders, the right was further away from ideal. Just take another reading like you did last time.

I had no perceptible power loss, no flashing CELs, no misfires, etc. when my cats started throwing codes. When we took off the right one, we could see it was falling apart. My mileage has been steadily improving since.

I switched from Shell to ExxonMobil for my last 2 fillups after what u said about them. Go figure my fuel mileage has crept up another 2mpg. I swear that Shell crap is a lower octane even though they show it as 93 and I only run 93. The truck don't even sound the same and feels like its makimg more power which leads me to believe what u said about shell.

My truck is tuned with a cam and all but before the switch I could barely hear the lope of the cam until after longer drives. Now I hear it after getting to the first stoplight..definitely not a placebo effect..

I'm currently seeing 12.5city with a 3k stall with 4l80 and 3.42 gears. Its probably the worse combo for city driving so there has got to be something up with the OPs truck. my hwy mileage is around 18-19mpg cruising 80mph which may be even better after switching fuels.

Sent from my SAMSUNG-SM-G900A using Tapatalk

 

[swathdiver]

I switched from Shell to ExxonMobil for my last 2 fillups after what u said about them. Go figure my fuel mileage has crept up another 2mpg. I swear that Shell crap is a lower octane even though they show it as 93 and I only run 93. The truck don't even sound the same and feels like its makimg more power which leads me to believe what u said about shell.

My truck is tuned with a cam and all but before the switch I could barely hear the lope of the cam until after longer drives. Now I hear it after getting to the first stoplight..definitely not a placebo effect..

That made my day, thanks for sharing!

 

[Scottydoggs]

for sure all gas is not the same, i found that out real fast.

frigging 93 just hit 315 here. im not to happy about that.

 

[HiHoeSilver]

for sure all gas is not the same, i found that out real fast.

frigging 93 just hit 315 here. im not to happy about that.

Wow. I pay 3.25 for 89. The 93 is 3.90

 

[Scottydoggs]

Wow. I pay 3.25 for 89. The 93 is 3.90

it was down to 240 ish all winter, then they added a 22 cent tax, now summers here and of course gas went up as always. for NJ being such a hell hole we still have pretty low gas prices and we cant pump our own gas, so full service at that price.

so a 60 cent gain is a kinda a hit. this just makes me drive my regal more sadly. im tuned to use meth injection. glad i got 14 gallons sitting here, ill kill a gallon over 2 weeks time just driving to work, and the only place to buy it is at the track. i run 93 im the hoe too. but the hoe drinks it faster. so little hot rod it is......14 gallons just cost me 42 bucks. that will last me a month roughly.

 

[BlueCollarTahoe]

Compared to your left bank of cylinders, the right was further away from ideal. Just take another reading like you did last time.

I had no perceptible power loss, no flashing CELs, no misfires, etc. when my cats started throwing codes. When we took off the right one, we could see it was falling apart. My mileage has been steadily improving since.

okay cool so heres an update. i hooked up the ancel and the torque pro with the bluetooth adaptor to compare and the numbers were the same. i took a bunch of screenshots from when i left work, highway driving..car off..then at idle again. i found a table of whats considered the various loads to diagnose the fuel trims properly so tomrroow i have those numbers in the proper loads.

now thats not my car that was some caer they used but now i see whats the different load amounts and can get that. but i did notice something...at idle after i parked for the night
STFT1: -0.78
LTF1: 7.8
LTFT2: 9.4
STFT2: -2.3%


arent these numbers supposed to be as close to 0 as possible at idle?


earlier in the day after the highway driving:
LTFT1:0.8%
LTFT2: 0.8%
STFT2: 2.3%

also ive gotten a PO455 CODE on and off...i replaced all the compnents and the gas cap in the evap system and still get it once in a while. saw this in the Emissions rediness s/DTC table:

Evaporative system: incomplete
02 Sensor incomplete

the rest of them ) misfire/fuel systemm compnenets, catalist) said complete or not availble. now i know if i got a large leak somewhere then yea the evap system may not be complete but the 02 sensor being incomplete? or are they connected? i also have 1/4 gas tank today i think ir ead somewhere the tank needs to be 3/4 or full for the evap system to work properly not too sure about that tho.

 

[Scottydoggs]

evap and the o2 can take a while to become "ready". like days even.

your trims really dont seem all that bad, they come with a lean ass tune stock. mine was +8 all the time before i tuned it.

when on a cold start the trims are not true. the engine is running off pre set settings till it warms up, then it runs off the sensors. and then trims are really what they say.

we no longer have a choke, so the pcm adds fuel to make it run when cold, so you get that high idle as well. why the trims got neg numbers on the cold start.

 

[swathdiver]

The one thing I see compared to last time is that his right bank is a little off from his left. So was mine when the cat was on. Haven't really monitored it since that last posting. Heck, haven't drove it in weeks.

 

[BlueCollarTahoe]

well may turn out just to be city driving getting me....but i will post all the trim numbers monday hopefully. been a long couple days.

 

[sonic_the_hedgeh]

so for a while i been getting more or less 8 mpg. when i fill the tank it usuallt says around 208 210 estimated miles. last tank i got 218 before i chickened out and filled up. i run all terrains on the factory 17. nothing crazy. i think this is low. i took it to my shop the guy the said the computer was all messed up and reprogrammed it. it worked some i was getting another 1/4 tank more or less. but even for city driving it still feels low. where do i start to figure this out? is this just the truck or is something wrong?

I would try seafoam intake cleaner. Safe to use and it could help.

Sent from my SM-G935W8 using Tapatalk

 

[BlueCollarTahoe]

I would try seafoam intake cleaner. Safe to use and it could help.

Sent from my SM-G935W8 using Tapatalk

have done it before didnt make a difference.

 

[BlueCollarTahoe]

UPDATEs with fuel trims:

idle with car at op temp:
STFT1: 0.00
LTF1: 4.69
STFT2: -0.78
LTFT2: 8.59


25 MPH:

STFT1: -3.12
LTF1: 8.59
STFT2: 4.69
LTFT2: 11.72


45 MPH:
STFT1: -3.12
LTF1: 9.38
STFT2: 2.34
LTFT2: 11.72


65 MPH:
STFT1: -4.69
LTF1: 11.72
STFT2: 1.56
LTFT2: 14.06


then noticeed crusing around 50 mph:

STFT1: -6.25
LTF1: 17.19
sTFT2: -3.12
fTFT2: 17.97


now i been having on and off an evap code, PO455 and ive changed all the hardware in the system ( the canister/vapor things the one in the engine bay and he one next to the canister)


i looked in he vehicle test results on torque pro and sawe that i got a NOT OK on the lean to rich sensor thereshold
min:32878
current 32771



any ideas where to look from this info?