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2004 Ford F-350 v10 low power, bad mpg, no codes, starts great


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OldGuitarman
New User

Mar 12, 2018, 12:20 PM

Post #1 of 2 (1814 views)
2004 Ford F-350 v10 low power, bad mpg, no codes, starts great Sign In

I've been around the block a few times and twisted a wrench or two in my younger days but this trucks issues aren't making any sense to me. The problem is this. i bought the truck used from a dealer 6 years a go. The truck had say 180000 miles on it. Since then i have put roughly 25k on it. i use my truck as intended, but i don't abuse it. it gets yearly maintenance and high octane gas. the truck has done everything i asked with no issues. About a year ago i noticed the fuel economy starting to decrease rapidly, i know its a fuel pig but went from approx 11-12mpg to roughly 4mpg. the mil light has not been set, there are no code pending or otherwise. to make a long story short here is whats been done.

1. replace all plugs (replaced with OEM) and boots
2. all injectors have been pulled and verified working within specs (ohm check) replaced all o rings and wiring checked with a node light.
3. fuel pressure verified within spec replaced any way. last ditch effort.
4. new red top battery and terminals and alternator.
5. had intake (both) and Throttle body/plenum gaskets replaced.
6. checked wheel bearings\ brakes\ steering components for binding or wear. had alignment checked no abnormal wear on tires.
7. o2 sensors replaced.

This the odd things that i noted while my scanner was hooked up. first of all the truck is not running a obd II its a old modified obd I ecm firmware running the newer dtm hardware. It only has o2 sensors before the Cat. they use a o2 sensor bank one s1 and s2 bank 2 is not used. there isn't a cat heater. So there wasn't any data as far as fuel trim on bank 2. but all in all the data seemed normal. the only things i thought was unusual was the TPS switch at idle was at 20% and the calculated load on the engine was 40-45% . Engine idle was 1100 closed loop and about 600-750 open loop. oh yeah temp is normal oil pressure is high and steady. not eating oil or puffing out any determinable smoke light or dark smoke and there is no sucking at the tail pipe (with hand over end) good back pressure, transmission shifts smooth and positive doesn't over heat. no foreign bodies in oil, radiator fluid or axle\transfer case. The truck just doesnt perform well and is eating gas like a over loaded RV going up wolfcreek pass.... in reverse. The dealership and me have gone rounds Because they try to feed me a line of crap every time i have to use their services and are constantly experiencing I D 10 T failures every time i go there. Like telling me that i needed a oil change when not more than 4 hours earlier i did all my fluids...myself. and said there scanner didn't reveal anything unusual. Even though i disconnected my o2 sensor and remove my air filter in the parking lot and wanted to charge me 1000. bucks for 2 days diagnostic. So .... anything would be helpful,
thanks for help in advance.

HELPCrazyDriving MadMeWinkFrickingTongueCrazy


Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Mar 12, 2018, 2:05 PM

Post #2 of 2 (1804 views)
Re: 2004 Ford F-350 v10 low power, bad mpg, no codes, starts great Sign In

If I remember right, 20% TPS on a ford isn't unusual. According to service information the TPS voltage should be between 0.53-1.27 volts key on engine off. The engine load calculation seems high for idling. It should be somewhere between 14-16 at a hot idle.

What is the MAF sensor voltage with the engine off key on?

There should be a pid for bank 2 fuel trim. Even though it has OBD1 software it still should be monitoring both banks fuel trims.

What are your long and short term fuel trims (average) at idle and while cruising?





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Mar 12, 2018, 2:06 PM)






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