Hi Guys,
I'm out of answers as to how to find this problem. I've been messing with lot's of little things. I thought I had it fixed. It runs great. Timing is at 12 degrees btc. I've got new plugs, stator in distributor, control module, new coil, new wires, new fuel pump, new power steering pump, newly ran harness for ignition because coil clip broke in half, new vacuum lines new fuel lines new air filter, new fuel filter in-line between pump and carb, and new screw in filter at carb. This was all done in the last month. It finally ran great for a week now, until today when I went on the freeway for the first time, for one exit. It reached freeway cruising speed, then-whamo, had no response from pedal, acted like a chain saw if you flipped the choke on after it's already warmed up. I kept trying to feather the pedal hoping it's some clump of dirt needing to pass. Pulled to the side to let traffic go by, hit my hazards, I could sense the motor died. So put it in neutral and started it. It fired right up, coughed and sputtered, then seemed to clear. By this time I was almost at a stop. Placed it in drive and it ran like a top. I took the exit which I'd almost reached. I was hesitant to push the speed past 40. I also didn't accelerate fast to reach the 45 speed limit. It reached it but seemed like it wanted to repeat but it didn't. I had to get through three red lights and a left turn light. It ran beautifully and idled fine waiting for the green. On one light I had hoped to make, it turned yellow too soon so I had to brake hard and it handled that fine. Never coughed, or sputtered. Even has quick response when light is green. No hesitation. Ran awesome. Got to work. Worked. Headed home. Took another backroads way so I could get up in MPH. It ran beautifully again....until I hit about 55 and it bogged hard on me again. This time it didn't die. I pulled to the side and hit the hazards again. When I'd reached about 10mph it seemed to act like it would be fine again. It was. I went up and waited for 2 red lights, idled fine, made it home, ran great.
In 10 years I'venever yet rebuilt the carb. From what I've read it's the float, or something sticking in the bowl, OR...I've replaced the gas lines in the engine bay but the rubber line on top of the tank still never messed with, also never dropped and cleaned the tank. Maybe it never has had that done. Could be sucking air through a dried out fuel line??when I'm going that speed. Any thoughts.

 

I have had the little rubber hose between tank and hard line go bad and cause almost the same thing.

Around town ran fine but getting on the high way with short blending area and up hill too the car would die like out of gss.
Replaced that short hose and all was good as gain.
Dave - - - -

 

Agreed! There are actually 4 hoses on trucks with dual tanks: tank to line; line to valve; valve to line; line to pump. The hose used then was not designed for ethanol, and the rubber will break down with today's fuel.

 

Like battery cables gas hose you can't tell by looking at them if good or not as both go bad from the inside out.
Dave - - - -

 

That's good advice. I need to do this then, for many reasons. Is it doable without dropping the tank? BTW- Will the tank eventually need to be maintained. Single tank truck. I think even to drop the tank it requires that hose clamp and rubber line removed first. Am I right? Anybody have a good link to a tank maintenance DIY? Thanks for replying. I realize I'm not helping myself putting these tasks off for later. I just need to drive it to work today. I think I'll take the road through town instead of the freeway, today.
Also, can I rule out the EGR? Wouldn't the EGR problem be opposite? Sticks open when slowing to idle? If it stuck closed, what would that do to WOT? Nothing right? Just curious. One last concern is when I replaced fuel pump I hooked it up backwards at first and kept trying to prime it. Felt foolish when I saw the 'IN' on the line going to carb. I could have sworn the hard line to tank went to the welded nut on pump. Would any damage I may have done cause this highway prob? Seems the fuel pump would either suck, or not suck.

 

A bad fuel line can cause this, as previously mentioned. Also, perhaps the tank is not vented properly... this will create a vacuum which can restrict fuel flow to the carburetor. Does the fuel line come into close proximity with the exhaust [vapor lock]?

 

Probably didn't hurt fuel pump any, they don't care about that. But your carburetor might care that you have a different fuel pump. Output and pressure is bound to vary, consequently anytime the fuel system is serviced it is wise to check fuel height in the carb bowl. Just WAG, but it could be the engine is starving for fuel at higher speeds.

 

Thanks for the added remarks. Now, it's got to get me there and back one more time. Fingers crossed.

 

If it bogs down, again, try loosening the fuel cap and listen for a hiss [air being sucked in].