'85 Chevy Suburban coughing-help!

[DarkAngelGStudy]

Hi, all,
I'm new to this forum, just discovered it.     I'm hoping someone here can help me out with my truck.  To make a really long, expensive story short, my truck has some kind of a cough...it will cough and sometimes stall when I'm driving it.  I've put about $1400 into repairs, and it was fine for a few months, but now it's starting up again.  I have rebuilt the carb, replaced the fuel pump with an electric one, tune up, stp gas treatment, had vaccuum lines checked, replaced electrical wires, replaced the fuel filter, and it purrs like a kitten when idling or running.  It only coughs and stalls when I'm driving, not sitting.  I'm also noticing that this is more frequent when the weather is hot...but my truck is not overheating.  I've had it into several mechanics, including the Chevy dealership mechanics...they drove my truck for literally 50 miles and nothing happened (of course!).  This after I literally limped the truck to the dealership!  I am at my wit's end...can someone here please give me some suggestions?  HELP!  
My truck is a 1985, with the 454 V8...largest engine, I think it's the 7.1 litre?  I can't afford to buy another vehicle, I'm a single mom.  I appreciate all helpful suggestions, thanks so much!    

[fibertek]

Do you know what kind of distributor is on it?  Mine had a problem like you were describing, and it ended up being the distributor.  There is a mechanism under the rotor that get sticky/dirty and needs to be cleaned.  It will not allow the timing to advance or retard as it is needed, but only periodically.  You can clean it up with WD-40 and it will keep from sticking.  You can try that, or even swap out for a good distributor.  Hope this helps.

Jason

[bangburban]

first suggestion: bad coil. if your coil is bad, a few degrees of temperature rise can raise resistance and cause intermittent stalling. easy fix - replace coil (it is in the distributor cap). second suggestion: there is a 1/4" return fuel line that runs from the original mechanical fuel pump to the gas tank. this line was meant to prevent vapour lock problems by supplying cooled fuel. if your truck is experiencing vapour lock, especially in hot weather, you can have surging, sputtering or stalling. check to see if this line is okay - not pinched, rubber flex hose okay, etc. you may not have had to replace your pump if this line is affected - it could be just the line.  

[Mr Diesel]

Dude, she wrote that post more than 2 years ago. The thing is probably fixed by now....

- Mr Diesel
'76 C30 Crew 6.2