1979 F250 400/6.6 4x4

This just started.

I accelerate and the engine stumbles. If i keep the accelerator depressed, it will lunge forward.

 

Shhhhh, kiddo. Momentum isnt a theory. Are you trying to say momentum theorum?
And tbh, i used Google for that...

 

I went to the dentist, drove home and no issues.

 

Fuel filter ?, run a can of Sea Foam and Heat thru the fuel tank ? Accelerator pump on the carb in good shape?

Air, fuel or fire, problem has to be one of the 3.

 

Fuel filter is brand new(2 weeks). I adjusted my carb to the highest vacuum about a week ago. I read a site that talks about "puddling".
Since it started out of the blue, and ended just as fast, maybe thats what is going on?

http://www.thecarburetorshop.com/Troubleshooting.htm

Accelerator pump is bad if it is bad, plugs are bad if they are bad, carb settings are bad if they are bad, none of those would suddenly get better correct?

I had 3 wisdom teeth pulled today, so tomorrow off, i will recheck my idle mixtures

 

Maybe electrical if its intermittent ?

 

Idle mixture is unlikely if it was running fine before. Check for dirty distributor cap and rotor conductors, vacuum leaks, and fuel filter. Stumbling on acceleration is possibly an accelerator pump issue. Does it have a strong immediate squirt in the intake when the throttle is depressed? Ethanol fuel can eat the diaphragms and other carburetor soft parts.

 

Fuel filter-2weeks old
Cap rotor-6 months
Carb-rebuilt little over a year ago
Vacuum lines-mostly replaced

But....
I will take em one by one and run through em tomorrow. If it can break, it can get fixed!

 

This started again yesterday.

In park or neutral, it idles great. As soon as i accelerate, it hesitates and lunges. If i press down on the accelerator, it sounds like the engine is winding up but its buckin to catch up.

Today, i replaced all the plugs, which werent bad. New air filter. Checked the oil level, clean and correct. Checked tranny fluid, no foam, clear red and correct level.

My vacuum is steady at 18.

Accelerator pump is pushing 2 straight streams

I had filled my tank at a local Arco. Then drove about 15 minutes to the bank. I came out and started up fine, drove 2 minutes and it went from great to this. I immediately pulled over and it was about 5 minutes before it would start. I limped it home.

Would this sound like the torque converter?

 

Still sounds like the carburetor. I had this going on with my LTD, intermittent stumble on acceleration; accelerator pump looked fine. I finally just rebuild the carburetor. When I had it apart, I found debris in one of the idle transfer slots. After typing this, I re-read and see that you already built it, but there still could be an issue.

If it were transmission related, the engine would rev up like it should, but the vehicle wouldn't go. You're saying the engine itself is bogging down; that's completely upstream of the transmission. The reason it doesn't happen out of gear is because vacuum is higher and the engine is unloaded.

 

I didnt rebuild the carb. The PO said that it was rebuilt in the 5 months that he had it.

I will look for a rebuild kit.

 

In that case, I'd consider it "not rebuilt." Who knows how he did it. You'll want to do the full Chem Dip job (dip, spray out, etc).

 

Boom!!😃

I reread the comments and went ahead and opened up the carb to see if there was anything obvious amiss.



I dont know when or how...
Musta been when i changed the filter? Im not sure. There is a piece of what looks like a bugs wing, covering up the up jet!! I used a rag to soak up the gas, and Qtips to swipe any other debris out.

Thanks for all your help!! Again