Bucking bronco

[militarypotts]

I'm hoping someone out there can come up with an answer to my recent problem.
Last Friday I was on my way to our local cruise night. Going down the road at 35 mph, my truck suddenly started to lose power and started to buck wildly. I was in 4th gear at the time. I put in the clutch and pulled over to the side of the road. Stopped the truck, but never turned the motor off. Started to drive again and about 5 minutes later it started to lose power and buck again. I thought maybe I miscalculated my fuel level, (my gauge doesn't work, so I go by miles driven) and pulled into a gas station and put in $20 worth. It then ran fine all the way to the cruise parking lot. Upon leaving a few hours later, it ran perfect until I got 2 blocks from my home and it started the same bucking routine again. When I got home, I let truck idle in front of the house and it idled absolutely perfect, not a single sputter.
Electrical problem??? Fuel delivery problem???
Thank you.

[Barrman]

Blow some compressed air into the fuel tank through the pickup hose. Just a guess but I had similar issues with a clogged pick up sock.

[kwai]

Actually sounds more like the clutch is slipping. You been riding it? Does it smell burn't.

[militarypotts]

Never ever ride the clutch kwai. Driven manual tranny's all my life. No burnt smell either. The hardest work my clutch goes through is during parades. Clutch actually went through my mind also, but for the most part, the truck runs fine as I go through the gears.

[militarypotts]

I can give that a try Barrman. Truth is though, when I had the tank off and boiled and lined, I never remember seeing any type of sock over the pick up end of the sending unit.
Would you still give the air blowing a shot?

[militarypotts]

Is an electrical problem of some sort even a thought at this point? Just seems strange that the truck can move along so well, and just like that she starts bogging and bucking.
The perfectly steady idle is what has me confused.

[kwai]

Does the engine continue to miss (creating the bucking) when you push in the clutch or just under load with the clutch engaged.


another way to eliminate the fuel delivery is to strap a 5 gal gas can to the bumper. You can run the fuel line to the drivers side of the engine where the frame hardline transitions to a rubber hose going to the hardline on the engine block.

You can check the clutch/flywheel by dropping the dust cover, you don't have to remove the tranny.

[jeeper]

The losing power first has me thinking fuel as well. I don't suspect the clutch by your description. I would think if it were clutch it would start slipping and the engine would start revving but you didn't mention that.

And electrical doesn't seem likely because the problem isn't happening at idle.

[militarypotts]

The engine never quits running. When the bucking starts to happen, I put in the clutch, come to a stop, and then start out again. It moves fine for a short while and then starts the bucking again. This probably all sounds strange, but this just started happening last Friday evening. Never had a problem like this before. Whats got me even more confused, is the fact that at idle, the motor runs as smooth as can be. On Friday, the three times this happened were all while the truck was in 4th gear and moving forward at a steady speed.

[Nailhead]

The smooth idle says "fuel starving" to me: the fuel pump is delivering sufficient fuel to maintain a good idle, but is unable to deliver enough for the engine to perform under load. The delay in the onset of the bucking seems to me like the time needed to empty the float bowl and start starving for fuel.

HOWEVER, one question: you don't have some sort of electronic ignition, do you? This also sounds like what happened when the ignition module on my M886 went TU: it would idle, but wouldn't perform under load, for some reason.