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Old 01-03-2008, 03:04 PM
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MPG meltdown

i have a 99 7.3 with 220K miles. i have the truck since 2000 with 30K. in recent months my mpgs have really decreased. when newer i got between 18-20 mpg. then dropped somewhat to around 15 pretty consistantly. now i am barely getting 10 mpg on the highway and the problem really seemed to show up and accelerate in the last 6 months to a year (approx 25 k miles). power seems normal. i have a K&N filter but other than that, no modifications. i am not leaking any fluids and dont have any warning lights on. my driving habits have remained constant. i almost always drive with hubs unlocked. rear is 373 (pretty sure). is this normal for a 7.3 with 220K miles or are there things i should be checking. also, i have never added any type fuel additives or oil additives, injector cleaners etc. i use rotella oil, same as always. i did post in the past and the forum nailed my problem. i hope you guys can help me again. thank you very much for any info provided.

jeff
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Old 01-03-2008, 03:07 PM
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when was the last time you changed your fuel filter? also winter blends fuel will decrease your MPG.....
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Old 01-03-2008, 04:05 PM
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also, i have never added any type fuel additives or oil additives, injector cleaners etc.

Filters first ...and try something like powerclean "douple dose"!
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Old 01-03-2008, 04:12 PM
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fuel filter changed within the last 3 months. and i will try some powerclean. thanks!

jeff
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Old 01-03-2008, 04:18 PM
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i have the same problem, and I have 230k.... i would like some help too, I use diesel kleen and change fuel filter every other oil change, which is at 3k
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Old 01-03-2008, 06:49 PM
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Smile

Another basic item...the tire pressure drops in your tires with the colder weather. Its an especially imortant factor with the heavier trucks and thicker ,stiffer sidewalls .Trouble is the engines are too strong for you to notice the higher rolling resistance.
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Old 01-03-2008, 06:53 PM
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id say there is about a 90% chance the o rings need to be changed on the injectors. The 99's had the old style o rings and they fail easier than the newer ones....and whent he copper crush washers on the tips fail they tend to really reduce fuel milage....Also, the o rings themselves can affect milage if the high pressure oil system isnt functioning to its full capability.....

Honeslty, there is no real diag for this, its just kinda a gut call, but with over 200k, it honestly is more like "maintanence" than it is a repair, so if i was you i would just do it....
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Old 01-03-2008, 07:14 PM
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I was wondering if any knows how much new injectors(stock) cost for an 01 7.3L I am having the same problem with mine about 230,000 miles on it. Just figured that I would put them in myself and try and get some better mileage out of this awsome truck! Any special tools needed to change them? Thanks for the help.
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Old 01-03-2008, 07:16 PM
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Quote:
Originally Posted by 01clj View Post
I was wondering if any knows how much new injectors(stock) cost for an 01 7.3L I am having the same problem with mine about 230,000 miles on it. Just figured that I would put them in myself and try and get some better mileage out of this awsome truck! Any special tools needed to change them? Thanks for the help.
you dont nessicarely need the injectors, just need to re o-ring them.....

There arent any special tools, but there is a VERY VERY presice procedure you need to follow when removing the injectors...
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Old 01-03-2008, 07:30 PM
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Marc thanks for you response I am not sure I understand how o-rings affect the performance of the injectors but I will take your word for it. Is the same procedure used to replace the o-rings as to replace the injectors and can that procedure be messed up easily causing major problems or is it easy if you follow some expert advice?
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