Engine surging at speed
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Cargo Master
Joined: Oct 2010
Posts: 2,339
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From: Lost In a Pit of Despair
Engine surging at speed
While driving home in my 76 F250 today, my 300 started acting up. When I hit about 55-60 MPH in 4th gear, the engine was turning 2800 rpm, which I'm assuming is normal. All of a sudden, the truck started lurching back and forth, and the engine threatened to die. I pulled off to the side, and nothing seemed to be wrong.
It happened a few more times, all at about 55mph. It didn't matter if I was going uphill, downhill, loaded or unloaded. And it's intermittent.
Now my gut tells me it's something having to do with fuel delivery. The other day I had some issues with rust getting knocked loose in the cab tank and plugging the inline filter I put in before the fuel pump just for that reason. At the time, something must have gotten past the inline filter and the one on the carb, because something plugged the jets. Turned the mix screw out a half turn and it cleared itself up. So I'm thinking maybe something else got through?
Any help is appreciated
-Jameson
It happened a few more times, all at about 55mph. It didn't matter if I was going uphill, downhill, loaded or unloaded. And it's intermittent.
Now my gut tells me it's something having to do with fuel delivery. The other day I had some issues with rust getting knocked loose in the cab tank and plugging the inline filter I put in before the fuel pump just for that reason. At the time, something must have gotten past the inline filter and the one on the carb, because something plugged the jets. Turned the mix screw out a half turn and it cleared itself up. So I'm thinking maybe something else got through?
Any help is appreciated
-Jameson
Cargo Master
Joined: Apr 2009
Posts: 3,038
Likes: 4
From: South west Idaho
I think you might be on the right track with the filters , all i can suggest at this time is to maybe change them out again. Then just keep changing them out until things clear up. The next idea would be to drop the fuel tank and clean or replace it because it sounds like there is rust and who knows what in it now.
Thread Starter
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Cargo Master
Joined: Oct 2010
Posts: 2,339
Likes: 32
From: Lost In a Pit of Despair
After I changed the in line filter the other day I filled up the aftermarket poly tank on the drivers side of the truck, and was running clean gas out of that when I was having issues with the surging.
Posting Guru
Joined: Feb 2009
Posts: 1,088
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Is the engine surging, like you are moving the gas pedal up and down, or is it more violent as if the engine is cutting on and off? If it's the latter, you might check the PCV valve. A friend of mine had this happen on a 240. It even took the mechanics at the local Ford dealership a couple of days to figure out, but once the PCV valve was changed it ran smooth as silk again.
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