Sudden power loss
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Cross-Country
Joined: Oct 2023
Posts: 62
Likes: 4
From: Monument, CO
Sudden power loss
79 F150, 351m. The other day when driving home, temp in the low 80s, down the interstate at about 70. The truck started a series of suddenly losing power and bogging down, then in a few seconds, picking back up again. No backfires, no idiot lights, temp gauge was fine, plenty of gas, radio etc still working. I managed to make it another 7 or miles or so to my exit, still with the occasional bogging. Got off on the road I wanted, and when going about 40, I did the same thing. This time I dropped down to 3rd to get and keep the revs up and got home. I had already driven the truck abt 40 miles that day with zero problems.
Looking for ideas before I dive into it. My first thought is something like a bad coil, I've experienced that before in other vehicles, but I also wonder about fuel pump, ignition module, something like that. Not sure if it was spark or fuel. Looking for some ideas, I've not had a Duraspark system before. I've owned the truck for a few years, and it's never done that.
Looking for ideas before I dive into it. My first thought is something like a bad coil, I've experienced that before in other vehicles, but I also wonder about fuel pump, ignition module, something like that. Not sure if it was spark or fuel. Looking for some ideas, I've not had a Duraspark system before. I've owned the truck for a few years, and it's never done that.
Thread Starter
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Cross-Country
Joined: Oct 2023
Posts: 62
Likes: 4
From: Monument, CO
Is it possible lack of a shroud is causing my problem? I'm unable to find an aftermarket shroud that fits my radiator correctly, and the used oem shrouds are in bad shape and brittle, so they disintegrate.
Cargo Master
Joined: Dec 2008
Posts: 3,213
Likes: 321
From: SW PA
Check/replace the fuel filter first as already suggested and then report back.
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Hotshot
Joined: Feb 2004
Posts: 10,806
Likes: 2,604
From: The Shenandoah Valley
Was a good thread here.To shroud or not to shroud - Ford Truck Enthusiasts Forums
and what I did after mine fell apart Fan shroud, yes or no. - Ford Truck Enthusiasts Forums
As to your power loss .... your issue might be the fuel filter or pump related, .... but it maybe Dura-SparkII related. I carry spares.
Last edited by tbear853; Mar 30, 2026 at 12:46 PM.
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Cross-Country
Joined: Oct 2023
Posts: 62
Likes: 4
From: Monument, CO
I think I know the problem!
Well, I finally got a chance to go out and really troubleshoot my problem, and I'm 99.9% sure I have the answer, after looking into it while the engine was running. The fuel pump (original to the truck) is leaking, a steady drip, drip, drip, once or twice a second or so at idle, so I have a new one on the way! I thought it would more likely be a fuel issue more than anything else, because the day the problem occurred, I thought I was getting a slight whiff of gas once in a while the day the problem happened while driving. I'm still going to go ahead and change out the fuel filter while I'm at it. I also have a spare ignition module and coil, but I'm not going to put them in right now, as I never really thought it was an ignition problem.
Thanks to everybody who offered suggestions. Been a LONG time (decades) since I've had to troubleshoot that kind of problem!
Thanks to everybody who offered suggestions. Been a LONG time (decades) since I've had to troubleshoot that kind of problem!
Last edited by Dano76; Apr 2, 2026 at 07:30 PM.
Fleet Mechanic
Joined: Feb 2004
Posts: 1,508
Likes: 332
From: Arlington,Wa
Change the oil before you drive it. When the fuel pump starts to leak...it also leaks internally leaking gas into the oil and it will eat the main bearings real fast. Ask me how I know...
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