Input on Fuel Mileage
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Senior User
Joined: Sep 2009
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Input on Fuel Mileage
Hello Everyone.
I have an early 99 PSD with 4R100. Notice over the past 7 months that fuel mileage has dropped. Here's the basics;
Truck currently at 250,000 miles. Last month major service completed which included new air, fuel, trans and oil filters. New engine oil and trans fluids.
Tires are stock, no peformance programming of the PCM. No check engine light. Last week changed out the fuel pump because of high mileage (250,000) and replaced/upgraded the grey CPS in 2006. When I bought the truck (used) in 2005 fuel mileage was about 20/21 MPG under 2000 RPM or 70 MPH. However, the fuel milage has dropped to around 15 MPG and when towing the gooseneck trailer or hauling the cabover camper the mileage drops down to 11MPG.
I noticed that upon accelleration a faint black smoke from the trailpipe and the inside of the tailpipe is dry and sooty (black)
Seems the truck is over fueling for some reason. Anyone one out there have the same problem? If so, what was done to repair it. At $4.00 a gallon would like to recover the fuel mileage once again.
Thanks in advance for all replies and suggestions.
jeff
Empty wallet in Nevada
I have an early 99 PSD with 4R100. Notice over the past 7 months that fuel mileage has dropped. Here's the basics;
Truck currently at 250,000 miles. Last month major service completed which included new air, fuel, trans and oil filters. New engine oil and trans fluids.
Tires are stock, no peformance programming of the PCM. No check engine light. Last week changed out the fuel pump because of high mileage (250,000) and replaced/upgraded the grey CPS in 2006. When I bought the truck (used) in 2005 fuel mileage was about 20/21 MPG under 2000 RPM or 70 MPH. However, the fuel milage has dropped to around 15 MPG and when towing the gooseneck trailer or hauling the cabover camper the mileage drops down to 11MPG.
I noticed that upon accelleration a faint black smoke from the trailpipe and the inside of the tailpipe is dry and sooty (black)
Seems the truck is over fueling for some reason. Anyone one out there have the same problem? If so, what was done to repair it. At $4.00 a gallon would like to recover the fuel mileage once again.
Thanks in advance for all replies and suggestions.
jeff
Empty wallet in Nevada
Senior User
Joined: Dec 2010
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All the crap they added in the fuel is about right now. I have exhaust intake and a 35 inch tire and get about 11 mpg no matter how i drive it. My dad has an 01 crew cab and we pulled a 30 foot trailer frkm pa to florida back in 2006 and got 22 mpg. Now his truck is about 12 as well
Senior User
Joined: Dec 2009
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From: Columbus, Ohio
13.14 driving down to RRE from Columbus with 6 passes on the drag strip. Got live tuned by Jody yesterday, will post when get back and fuel up Monday. Ran in 60Tow comming down, will try 60 Econo going home.
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From: So Cal Highland
Clogged EBP Tube/Sensor?
Welcome to guzzle's Exhaust Backpressure Sensor Cleaning Maintenance Web Page
Easy to perform, and no new parts!
Welcome to guzzle's Exhaust Backpressure Sensor Cleaning Maintenance Web Page
Easy to perform, and no new parts!
Logistics Pro
Joined: Dec 2010
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From: Temperance, MI
Clogged EBP Tube/Sensor?
Welcome to guzzle's Exhaust Backpressure Sensor Cleaning Maintenance Web Page
Easy to perform, and no new parts!
Welcome to guzzle's Exhaust Backpressure Sensor Cleaning Maintenance Web Page
Easy to perform, and no new parts!
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I checked the intercooler boots for wear and they looked good and I tightened the clamps to ensure no leaks. My definition of the up pipes would be the "Y" pipe behind the turbo that leads to the exhaust? That pipe and donuts were replaced this year. The old pipe itself was rusted through. I also checked the EBV tube and it was not plugged,just abit sooty inside. Cleaned that out and cleaned the sensor. I filled the tank and drove 4 days around town(no trailer or camper), start and stop driving then fueled again. Results 14.8 MPG still down from by 3 MPG from a year ago.
Inside of tailpipe black, dry and sooty. Also from a stop, accelerate WOT, black smoke can be seen coming from the tailpipe leading me to believe there is an over fueling condition.
If the PCM, CPS and EBV sensor control fueling could one of these items be at fault? If so, no SES code is thrown.
The injectors have 250,000 miles on them and have never been removed. Could the injectors be at fault?
Inside of tailpipe black, dry and sooty. Also from a stop, accelerate WOT, black smoke can be seen coming from the tailpipe leading me to believe there is an over fueling condition.
If the PCM, CPS and EBV sensor control fueling could one of these items be at fault? If so, no SES code is thrown.
The injectors have 250,000 miles on them and have never been removed. Could the injectors be at fault?
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Joined: Aug 2010
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Honestly I think your current mileage sounds about normal. I have an e99 and even with 95% highway cruising at 70mph I'm averaging 17-18mpg. Todays diesel is garbage compared to a few years ago, which is what I blame for the bad mpgs...
Lead Driver
Joined: Sep 2005
Posts: 9,399
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From: Norco,CA
On my E99 dually around town is about 14 plus with 4x4 4.10 gears lb cc. When I changed my HPOP to terrminator t500 it got a lot better and, I do have a tuner DP, at 78mph on the freeway I gained 2 MPG + way more pickup and go. I always recommend this mod to everybody who has an early 99. Your 15 pump was weak from the begaining and with 250,000 on the clock its more then time. I don't believe you have to have a tuner to get benefit from this pump. They changed to a 17 on the late 99's for a reason. Again what everybody above said about the fuel is right. Summer blend especially.
Chet
Chet
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One last question, I checked the exhaust and found that the muffler has rust spots starting, which would need replacing, Could the catalitic converter be plugged after 250,000 miles? I do run the stock exhaust. Please explain more about the HPOP to Terminator T500 and the 15 pump to 17 pump. I'm not familiar with this terminalology.
Jeff
Jeff
Lead Driver
Joined: Sep 2005
Posts: 9,399
Likes: 188
From: Norco,CA
One last question, I checked the exhaust and found that the muffler has rust spots starting, which would need replacing, Could the catalitic converter be plugged after 250,000 miles? I do run the stock exhaust. Please explain more about the HPOP to Terminator T500 and the 15 pump to 17 pump. I'm not familiar with this terminalology.
Jeff
Jeff
I am running my CAT to and stock exhaust which I intend to correct with other updates to the engine.
Chet
Senior User
Joined: Sep 2006
Posts: 158
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From: Texas Gulf Coast
Mixed highway and in town I am getting about 16-17. That was with 35" tires. I just recently switched to stock 16" rims with 285/75-R16s and I am hoping mileage improves a bit.
Right now the tires are BFG A/T KOs, and I have been wondering if switching to Michelin M/S 2s would help mileage any. Any opinions on that?
I think it is worth mentioning that if possible when measuring mileage that you should go back to the exact same pump you filled the tank up at. I was celebrating how great the mileage was when babying the throttle (19.X mostly city) and thought "this can't be right". I went back to the station down the street ($.10 more/gal) where I originally filled it and it took almost 5 gallons! The tanks on these trucks are really long and a slight grade can really affect how much fuel they will take.
Rick
Right now the tires are BFG A/T KOs, and I have been wondering if switching to Michelin M/S 2s would help mileage any. Any opinions on that?
I think it is worth mentioning that if possible when measuring mileage that you should go back to the exact same pump you filled the tank up at. I was celebrating how great the mileage was when babying the throttle (19.X mostly city) and thought "this can't be right". I went back to the station down the street ($.10 more/gal) where I originally filled it and it took almost 5 gallons! The tanks on these trucks are really long and a slight grade can really affect how much fuel they will take.
Rick