'02 7.3L, runs well, sudden loss of economy - Ford Powerstroke Diesel Forum
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Old 06-04-2013, 03:45 AM
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Unhappy '02 7.3L, runs well, sudden loss of economy

'02 F250 Lariat Crew SB, 2wd , 7.3, 240K miles.
Daughter ran it out of fuel, after refueling and running the air out it seems to run well, but fuel economy is abruptly reduced by full 25%. The tank of fuel that was exhausted gave 17.7 mpg in combined city/hwy mileage. First subsequent partial (1/2) tank, all city/suburban driving gave me just 12.8 mpg. Second partial tank after fuel exhaustion incident gave me 18.1 mpg in all rural highway driving, at 58 mph.
I used to get 16.3 mpg city/suburban, now just 12.8 mpg.
I used to get 23.8 mpg highway, now just 18.1.
Computer diagnostics say fuel system is working well, and no trouble codes found. I can't detect any loss of power, nor is it emitting any smoke, except if I really hammer it, and even then it is very little, just as it has always done.
I haven't hooked it to my 7,000 lb camper to check for power loss while towing, but I will do so this weekend. (I historically have gotten 13.6-14.1 mpg pulling a 27' travel trailer with having two 500 lb motorcycles in the bed, down here in flat Florida)
Ideas?
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Old 06-18-2013, 11:10 AM
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Check all the tubes running from your air filter and make sure they are connected well, also check your fuel filter and make sure your getting good flow
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Old 01-28-2014, 04:41 PM
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Did you ever find out the cause of your sudden mpg loss? I have an 02 F250 7.3L and just noticed a 5 mpg loss.
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Old 01-28-2014, 07:49 PM
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Quote:
Originally Posted by bloomingdale View Post
Did you ever find out the cause of your sudden mpg loss? I have an 02 F250 7.3L and just noticed a 5 mpg loss.
Quote:
Originally Posted by bloomingdale View Post
Did you ever find out the cause of your sudden mpg loss? I have an 02 F250 7.3L and just noticed a 5 mpg loss.
Nope. I ran fuel system cleaner through, changed the fuel & air filters, no improvement. I used the truck to pull the camper to the Florida Keys with the motorcycle in the bed, a 2000 mile round trip, and instead of 13+ mpg, I got only 10.9.

On a tip from a marine diesel mechanic, I mixed a 30 gallon barrel of fuel with 27 gallons of No.2 diesel, 2 gallons of ethanol-free gasoline, 2 quarts of Dexron II transmission fluid, and 2 quarts of PowerService Diesel Fuel Supplement (same company that makes Diesel Kleen).
With one complete tank full of this mix, my next full tank after that saw in-town mileage had improved to 15.4 mpg, and highway mileage was at 18.8 according to the on-board computer. I averaged 17.3 for the full tank, of which slightly more than half was interstate mileage at 64-65 mph.

Went to have a complete computer diagnostic done at the Ford dealer, where they hooked a laptop to the truck and did static tests, and then drove it for 40 miles both in the city and on the highway. Their diagnosis is that I have "eroded and worn injectors", and they need replacing or rebuilding, and that I should "consider replacing or rebuilding my High Pressure Oil Pump" as well, even though it tested out perfectly. Total estimate: $7185.

I don't think so.

I have 250,000 miles on the original injectors, and can have rebuilt injectors installed for $1650 at the most reputable diesel shop around, including a 1 yr warranty on parts and labor. They said if the High Pressure pump works fine, don't try to fix it, as it should be good for 500K to 1 million miles or more as long as I keep changing the fuel filter regularly and run good fuel.

I told them I'd bring the truck in for injectors in April.
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Old 01-28-2014, 09:02 PM
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The on board computer on the roof is unreliable. It is almost always off. Hand calculate your fuel mileage from now on for accurate results. 23 MPG even in the best of conditions is a stretch, even if your were 2x4 and manual
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Old 01-28-2014, 10:56 PM
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ya i average between 13 and 14 mpgs....

winter fuel kills mileage, clogged ebpv tube and sensor kills mileage.
try cleaning the tube and sensor as a start+

worn out injectors and hpop definately kill mileage
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  #7  
Old 01-29-2014, 04:29 AM
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Quote:
Originally Posted by peter379 View Post
The on board computer on the roof is unreliable. It is almost always off. Hand calculate your fuel mileage from now on for accurate results. 23 MPG even in the best of conditions is a stretch, even if your were 2x4 and manual
Those calculations are based upon dividing miles traveled by gallons used. I do use the on-board computer to get me a rough idea of fuel usage data, and will reset to get an idea of mileage over a shorter stretch.

It is 4x2, but auto trans, and 23 mpg was actually easy to get on long trips at 58-60 mph. That's not based upon the computer, but on actual fuel usage. Computer would usually tell me less, in the 21-22 mpg range, but when I calculated it, the actual mileage was better.

I drove to Brunswick, Ohio from Crystal River in central Florida, 1051 miles total, in 2010, and used just 44.2 gallons of fuel, total, for the entire trip up, filling up for only the 2nd time just 1/2 mile from my destination. That's 23.77 mpg. Average speed while moving, according to the GPS, was 57.4 mph.
On the way home, I got only 21.4 mpg.

Best economy ever calculated was traveling from Ft. Walton Beach, FL to Pascagoula, MS and back, where I got 25.1 actual, averaging 54-55 mph. On the way there, the onboard computer showed 27.6 mpg until I got into town. Round trip, I used just 12.6 gallons of fuel. (I log the mileage of every tank of fuel.)

And for the record, it took me 2 years to learn how to drive it well enough to get over 21 highway mpg on a consistent basis. If you drive it like it's a gas truck, you'll never get over 20 mpg. The first year I had the truck, I averaged 15.6 in town, and only 17.8 on the interstate highway. I still drove 75-80 mph on the highway back then. Now, I know better.

The 7.3 is a very efficient engine when nothing is off kilter.
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Old 01-29-2014, 04:56 PM
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Thanks for the update Frank.
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Old 01-29-2014, 05:04 PM
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OVER SEVEN THOUSAND DOLLARS FOR INJECTORS AND HPOP????????????????

That's about 4500 too much brother. Go elsewhere and get a second opinion or you can pull your injectors, send them to someone like Rosewood and get a set of better than stock for like 1500-2000. A better than stock HPOP like terminator or adrenaline will cost you 500-600 ish.
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Old 05-22-2014, 12:39 PM
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Rosewood all the way. I did the budget rebuild and was out the door for $580
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