Low MPG

forddeerediesel

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Logan Co. Ohio
I have an early 99 f-350 4x4 with 162,000 mi. Very good, strong pick-up, but I am only getting about 10-11 mpg, pulling or not. Tranny rebuilt aprox 2000 mi ago and didn't improve milage. While the shop had it they coded the motor, told me that I needed #8 inj and a new ECU. wanted a second opinion- the 2nd shop told me that injectors were fine per a 'buzz' test and that there were no codes. Engine Ok. Also HAD a Trans comand module the tranny. After the test, I got in it to leave and put it in drive and killed the motor. They rechecked the codes---NOTHING. killed it 6-7 times and it worked fine. No problems since. After that I unhooked the command module, tranny was acting funny, and the first shop thought it was tranny, took it to the dealer- tranny has 36000 mi warranty - they said there was no problem. Had them recheck the motor--- no problems this time....Amazing, I didn't change a thing.... Looking for Ideas. yes the fuel filter is new, the air filter is clean, can sometimes hear the waste gate open and close, but not always. Had a superchips tuner in it, took it out. Had the Edge controller in it, will never do that again. nothing helps. hope to check the fuel pressure in it this week. What else should I be checking????? thanks for your help.:dunno -mad
 

forddeerediesel

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Logan Co. Ohio
also forgot, oil level is good. I am running John Deere 15W40+50. That is what we run in Everything, could this be a problem?
 

DaveBen

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I don't know about JD 15W40+50 oil. Try using Motorcraft 15W40 for an oil change and see if they helps. If not go back to the JD oil.

Dave
 

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