7.3 horrible mileage - Diesel Forum - TheDieselStop.com
'99 & up 7.3L Power Stroke Engine and Drivetrain Discussion of the '99 & up 7.3L Power Stroke diesel engine and drivetrain in the 1999-Up Super Duty trucks and Excursions. No gas engine discussion allowed except on transmissions and drivetrain that pertain to all models. Please confine discussion of topics in this forum to those items that are specific to the 7.3L Power Stroke engine.

 
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post #1 of 7 (permalink) Old 08-22-2019, 05:56 PM Thread Starter
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7.3 horrible mileage

I recently bought an early 1999 f250 XLT 7.3. this is my first diesel so I'm new to them. It runs great and seems to have plenty of power under acceleration. I calculated the mileage running stock size tires, and I'm only getting 8-9 mpg without towing anything. The previous owner has a 50hp tune on it from a tuner. Here are all of my syntoms that appear to be off.
-Plenty of blueish smoke on a cold startup for the first minute or less. It starts right away though with no hesitation
-intermittent slight but definitely noticable vibration at idle with a slight jump in rpm's when it vibrates
-if I rev it in park when it's warm, blue smoke will come out but this only happens when I'm in park. If I floor it when I'm moving, coal will come out as usual.
Any help would be great.
Thanks.
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post #2 of 7 (permalink) Old 08-22-2019, 07:23 PM
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How many miles on the truck?

2002 F350 7.3L / 4R100 - 4WD CC DRW 8 Box, AIH Delete, Gauges- Pyro, Trans Temp, Boost, Fuel Pressure, TS-6 tuner, Zoodad Mod, Mishimoto 31 row Trans cooler, Mobil 1 ATF, Trans return line ATF filter, Hutch/Harpoon Mod, Air Lift Load Lifter 5000 rear air springs, Rancho 9000 shocks, Timbrens on the front.
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post #3 of 7 (permalink) Old 08-22-2019, 09:06 PM
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Quote:
Originally Posted by Forester121 View Post
If I floor it when I'm moving, coal will come out as usual.
It shouldn't do that, unless there's a tune still on it. You may have a problem with the turbocharger.

If it has a vibration or stumble with rpm change, it's likely got a problem. A scan tool should come up with codes. Be sure to use a PSD capable scan tool - most auto parts stores won't be able to pull up the codes.

First truck -- 1929 Model A Ford pickup, restored from ground up. Wish I still had it!
'99.5 F250 PSD Supercab LB 4x4, ZF-6 w/SB Con OFE, 3.73LS, Boost & pyro gauges, Swamps S175/146 injectors, DP 80 HP Econo PCM (classic version
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post #4 of 7 (permalink) Old 08-22-2019, 11:17 PM Thread Starter
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There's 250,000 miles on the truck. Tonight I realized that the truck uses oil like mad. I drove it less than 600 miles so far and the oil reading on the dipstick is barely above the "add' mark now. When I got the truck it was at the "full" marking. I'm thinking about having a diesel mechanic or Ford take a look at it, so I can be sure of the problem before I go invest money into it. Not exactly sure though.
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post #5 of 7 (permalink) Old 08-22-2019, 11:19 PM Thread Starter
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Yes it has a 50hp tune on it, anyways that what the previous owner told me. I'm going to inspect the fuel filter soon to see how it looks. And where can I get one of those scanners? Possibly Ford or definitely a diesel mechanic would have one on hand.
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post #6 of 7 (permalink) Old 08-22-2019, 11:24 PM Thread Starter
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I almost forgot to add, I smelt the oil that I had drained since the level was too high when I first got it (I drained 2 quarts) then it read in the proper range. The oil has a diesel smell to it. This is the biggest of my concerns right now because I believe it's resulting in the other problems as well. I keep finding more and more wrong about the truck and I don't have the money to mess around with it until I get paid. I'll drive my other car around until I get it figured out .
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post #7 of 7 (permalink) Old 08-23-2019, 10:25 AM
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The first diesel can sadly include a pretty expensive learning curve.

Good idea to have a Diesel Mechanic give it a thorough inspection before you start sinking money into it.

Good Luck.


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2002 F-250 4x4 CC SB 7.3 PSD w/4R100. 182,000 miles.
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2002 F-250 4x4 SC LB 7.3 PSD w/ZF-6. 177,000 miles.
NOS Black CPS. ScanGauge-II. Bilstein 5100. Stancor GPR. Walker BTM. Noco Mod. Michelin Defender LTX 285/75/16.

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2000 F-250 4x4 SC SB 7.3 PSD w/4R100. 164,000 miles.
NOS Black CPS. Rebuilt Fuel bowl w/gold spring, 6.0 Cooler, Walker BTM, Stancor GPR, Michelin LTX M&S2.
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