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2002 7.3 Rough Idle, Knocking, and Loss of Power

inthefield

Red Skull Member
Joined
May 19, 2020
Member Number
279
Messages
97
Loc
Texas
Just trying to determine how fucked I am here, ran home last night in my 2002 F250 (164K well maintained) 110 miles of open highway running 75-80 like normal. Stopped to fill diesel before heading home and I noticed that it sounded like there was a slight miss while idling. Got back on the highway and it was noticeably lacking power, babied it the 3 miles home and when I stopped it has a very noticeable knock on the passenger side.

It's a spare truck, and I don't have any availability to tear into anything too far, so I'm probably gonna drop it off at a shop I've done business with in the past. Any common 20 minute driveway fixes I should try first?
 
inthefield said:
Just trying to determine how fucked I am here, ran home last night in my 2002 F250 (164K well maintained) 110 miles of open highway running 75-80 like normal. Stopped to fill diesel before heading home and I noticed that it sounded like there was a slight miss while idling. Got back on the highway and it was noticeably lacking power, babied it the 3 miles home and when I stopped it has a very noticeable knock on the passenger side.

It's a spare truck, and I don't have any availability to tear into anything too far, so I'm probably gonna drop it off at a shop I've done business with in the past. Any common 20 minute driveway fixes I should try first?
Click to expand...

Any CEL? Oil look good? All fluids where they're supposed to be and not mixing with each other? Can you do a cylinder contribution test to see what one is knocking? I'd look real closely at the valve cover gaskets for shorted pins, and the wiring harness going to them. If you get injectors wires shorting it will shut down that cylinder or sometimes even the whole bank of cylinders.
 
No CEL, No Smoke, and I don't have the ability to run a contribution test or to check fuel pressure. I went out and started it up to get the trailer unhooked and it idled and ran normal, pulled it up into the carport and replaced the fuel filter that had 6k on it, and started it up, and let it run. I got about a minute of normal idle before the miss showed back up, looked in the valley and on the valve covers and didn't see anything obvious as far as wiring making contact or wear spots.

I've never ran the fuel level down as far as I did last night, so I guess it's possible that the in tank pickups are clogged if it started pulling debris from the bottom of the tank, but at this point I'm out of time and I'm gonna turn it over to someone who fixes shit for a living.
 
If our 2002 7.3 gets below a quarter tank, it runs terribly. It clears up when we fill the tank, though.
 
DNL said:
If our 2002 7.3 gets below a quarter tank, it runs terribly. It clears up when we fill the tank, though.
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Well this may be the answer, and it seems I just didn't let it run long enough to clear up. Finally got around to taking it to the shop last week, and idled/coasted the first mile, and then poked along for the next. When I pulled up it was running great, walked in tossed the keys on the counter, and told him it was now an intermittent rough idle, and the circumstances around it . He threw the keys back at me and said you sucked air up into the fuel lines, run it. 300 miles so far and no issues.

I guess I'll have to really live by the old "doesn't cost any more to keep the tank full than it does to keep the tank empty" ideology with this truck.
 
2big bronco said:
It's really common for the fuel pickup tube to crack at about the 1/4 tank mark. They sell kits to chang it to a 5/8 stainless pickup.
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Here’s the real solution. I just keep the tank above half because I’m lazy
 
On my 05 Super Duty, the bottom of the original fuel pickup was broken off. I found it when I dropped the tank to install the Fass sump. It would have caused the truck to run out of fuel around a 1/4 tank had I left it that way. You may have the same issue going on.
 
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