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Discussion Starter #1
I've been having fuel mileage issues for a long time with my truck. About 54,000 miles or so, actually. Anyway, most of the time the truck is sluggish taking off and gets around 10-11 mpg. But, occasionally it will take off like it should and get around 17 mpg. This however doesn't happen often or for very long. Does anybody have any ideas, besides air filter and fuel filter, I've changed both, alot. Ive also replaced the MAF sensor. I have noticed that since the temp has been dropping here in Cheyenne it seems to run correctly more often. Sorry for the long post but I'm just trying to be as thorough as possible.
 

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Are you hand calculating the fuel mileage? the DIC is terrible, Look into the IAT sensor and fuel pressure regulator.
 

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Discussion Starter #3
no i'm just going by the dic, but with such a drastic change you can see the difference in how the fuel gauge moves when your driving on the highway. The IAT seems to read correctly when I'm looking at it with the scan tool. Do you think it can still be causing me a problem. A local shop in Cheyenne was just playing with the fuel pressure tonight with his modis and he looked at alot of stuff and said everything looked normal. But tonight happened to be a time when it was running good. Do you think the MAP sensor could be causing me a problem.
 

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Do a hand check and if it still sucks you might need to hollar at Rob and see if yall can't figure this out
 

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Discussion Starter #5
I've never actually checked it but on the interstate I've never gotten more than 400 miles on a tank from full to driving on the low fuel light, I've probably spent at least a couple hours on the phone with Rob. Its not easy over the phone with no codes.
 

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It could be from poor quality/bad quality fuel. Change stations/brands.
Stay away from thoses unbranded fuel stations.
 

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Discussion Starter #7
I've put my miles on this truck everywhere from detroit, to Corpus christi, to phoenix I can't even guess how many different stations I've gotten fuel from. At first I thought it was all because it was a stock truck so that's when I deleted it and now I can say for sure it has done it the entire time I've had it. Which is since it had 23 miles on it.
 

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Stock youll notice differences when its in a regen cycle. Deleted it shouldnt try to cycle. The low fuel light on these trucks comes on with around 4-8 gallons left depending on the truck so you cant really go by the gauge, they arent real accurate.
 

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You may check for threads regarding rear end chatter which can cause intermittent mileage and sluggish performance. There is also a TSB regarding this as well, I personally had my diff fluid changed recently and likely will have to have this TSB done as my fuel mileage and performance have suffered. My truck also produces a bit a grunt or grind when turning.
 

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Discussion Starter #10
I don't know what TSB means. My truck has only made a little noise like when you have a locker in the back turning a couple times. My problem seems to be a de-fueling issue. When the truck seems to be performing as it should it will puff some smoke, when its not running right there is almost no smoke at all, even here in cheyenne at 6500 ft. Stock trucks smoke more than mine does up here.
 

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TSB is Technical Service Bulletin... it is information designed to help both the technicians and consumers resolve issues.
 
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