Getting 8.5 mpg need help

[afpj]

The fuel trims you posted look OK. If you had a vacuum leak would expect them to be a bit off at idle. Someone mentioned it earlier but did you clean the maf and throttlebody? Check your brakes for evidence of dragging? Perhaps lift up the rear and turn the wheels to make sure the parking brake is not dragging as well? Just mentioning the simple stuff that I am capable of. I’m not a sophisticated type of dude, and I apologize if you’ve already checked those.

 

[bottomline2000]

The fuel trims you posted look OK. If you had a vacuum leak would expect them to be a bit off at idle. Someone mentioned it earlier but did you clean the maf and throttlebody? Check your brakes for evidence of dragging? Perhaps lift up the rear and turn the wheels to make sure the parking brake is not dragging as well? Just mentioning the simple stuff that I am capable of. I’m not a sophisticated type of dude, and I apologize if you’ve already checked those.

I was just about to mention this. If you have an infrared temp gun I would check the temp of each rotor after driving and see if one or more were excessively hot. (Harbor freight has one for a decent price, less than $20. I checked it against my digital thermostats in the house and its fairly accurate.) I did this after a major brake job and they were all fairly consistent in temp front to back around 80-100 deg but I have aftermarket drilled/slottted rotors but you get the idea.

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[swathdiver]

What is normal throttle plate percentage for GMT800? If that were a GMT900 that would be considered a little high and recommend to be cleaned. Mine was 7-8% during my tune and we cleaned it afterwards and it was down to 3-5%.

The snapshot of the trims doesn't really tell us much other than that they look ok. A snapshot over time would be better.

http://www.tahoeyukonforum.com/threads/fuel-trims-crazy.101453/

 

[BlueCollarTahoe]

The fuel trims you posted look OK. If you had a vacuum leak would expect them to be a bit off at idle. Someone mentioned it earlier but did you clean the maf and throttlebody? Check your brakes for evidence of dragging? Perhaps lift up the rear and turn the wheels to make sure the parking brake is not dragging as well? Just mentioning the simple stuff that I am capable of. I’m not a sophisticated type of dude, and I apologize if you’ve already checked those.

im gonna have them checked monday i replaced one caliper maybe a year ago and crazy enough this morning i got the scratching noise you get when the pads ar elow. these are relatively new Wagner pads. less than 10k miles on them. im starting to think the caliper they put on was put on wrong the whole time or something either way im gonna look at this. my ebrake things are rusted to hell but they still work lol and never apologize i appricate all of yall taking the time to help me out.

I was just about to mention this. If you have an infrared temp gun I would check the temp of each rotor after driving and see if one or more were excessively hot. (Harbor freight has one for a decent price, less than $20. I checked it against my digital thermostats in the house and its fairly accurate.) I did this after a major brake job and they were all fairly consistent in temp front to back around 80-100 deg but I have aftermarket drilled/slottted rotors but you get the idea.

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love harbor freight lol whats the proper temp? or jus tlook for one or two thats way off?

What is normal throttle plate percentage for GMT800? If that were a GMT900 that would be considered a little high and recommend to be cleaned. Mine was 7-8% during my tune and we cleaned it afterwards and it was down to 3-5%.

The snapshot of the trims doesn't really tell us much other than that they look ok. A snapshot over time would be better.

http://www.tahoeyukonforum.com/threads/fuel-trims-crazy.101453/

okay ill clean everything out again. the fuel trims over time i dont understand. should i record at idle and then whats the next interval? i can do it today

 

[BlueCollarTahoe]

also can a weak battery have influence on MPG?

 

[swathdiver]

the fuel trims over time i dont understand. should i record at idle and then whats the next interval? i can do it today

Ideally, your Long Term trims should be at or near zero all the time. If something is wrong, like an intake manifold leak for example, the LT trims will be in the high teens or greater at idle and come down while driving. Exhaust leaks can also skew the numbers.

Go for a drive and record, idle in park, in drive idling and then go for a short drive and womp on it if you can a time or two and then play it back when you get her home.

As for the battery IDK.

 

[bottomline2000]

also can a weak battery have influence on MPG?

Yes it can, but usually your alternator powers the vehicle while its to running. If it were bad you would see a batt light more than likely.

And yes, look for a wheel/s that is a lot higher in temp than the others.

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[mudpup]

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?

Try cleaning your mass air flow sensor, it helped on my 96 tahoe with the same problem.

 

[prrowe00]

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?

Did your say you got something reprogrammed? If yes
Check if you odemeter is reading a mile as a mile, test on interstate between mile markers or gps a location and compare actual mileage to google.
I had a truck once that the dash went out on and the new one was programmed for Kilometers.

 

[HiHoeSilver]

Try cleaning your mass air flow sensor, it helped on my 96 tahoe with the same problem.

I second this. A dirty MAF can screw you up. Also, a can of Kreen through the top end never hurts.

 

[BlueCollarTahoe]

cleaning the MAF tomrrow

 

[BlueCollarTahoe]

cleaned the throttle body and the MAF. idle seems a little smoother but MPG same more or less. working on thre brake thing tomrrow see if thats the culprit.

 

[BlueCollarTahoe]

took apart the calipers on back axle. turned out to be a peice of the dust sheild got bent and was hitting the rotor.i removed it, replaced all the break pads and metal clips on both sides and lubed all moving pieces. the break pads seemed normal except for 1 ont the inside on driver side. that one was oddly worn all the way down.

 

[BlueCollarTahoe]

where should i look next?

 

[swathdiver]

took apart the calipers on back axle. turned out to be a peice of the dust sheild got bent and was hitting the rotor.i removed it, replaced all the break pads and metal clips on both sides and lubed all moving pieces. the break pads seemed normal except for 1 ont the inside on driver side. that one was oddly worn all the way down.

Right there! If the pads were installed wrong the pad can wear down but it may be time for calipers. Was the dust shield on the same side as that worn down pad?

 

[BlueCollarTahoe]

Right there! If the pads were installed wrong the pad can wear down but it may be time for calipers. Was the dust shield on the same side as that worn down pad?

nah the dust shield touching was on the passenger side real axel. the worn down pad was the inside one on the driver side. driver side has no dust shield was removed at some point. i put in some all ceramic ones i got from AAP, the ones i had before were wagner thermoquiet ones looked like they were in there properly.

 

[swathdiver]

While I don't think those dust shields are killing your mileage, if it were my truck, I'd want them back on. How does the parking brake cable attach on the side with the shield missing? The really smart fellas will be waking up in a couple of hours, they'll shed more light on this.

 

[bottomline2000]

Right there! If the pads were installed wrong the pad can wear down but it may be time for calipers. Was the dust shield on the same side as that worn down pad?

Sounds like the caliper piston or slides were stuck in order for that to happen. I would watch that corner for excessive heat/drag.

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[BlueCollarTahoe]

Sounds like the caliper piston or slides were stuck in order for that to happen. I would watch that corner for excessive heat/drag.

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yea i greased all the pins and the new slides. weird thing my brake lights came on last night i check the brake fluid tank it was half empty. lights went off when i refilled but that was weird. i dont see any leaks anywhere. any thoughts where to look next in this chase after the MPG monster?

 

[swathdiver]

...thoughts where to look next in this chase after the MPG monster?

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.