1974 F100 starts to chug after 15 minutes driving although infrequently when driving at a slower pace. Would happen around the 70mph speed and stop chugs when slowed to 65mph. Any thoughts would be greatly appreciated

 

Replaced the ignition coil and spark plugs are in great shape, no leaks coming from fuel pump..perplexed!

 

Fuel Filter.

How old are the rest of the ignition parts Rotor, Cap, Wires?

 

Hey Ken,

Only have experienced this after it's been warmed up, in the past 3 sessions of driving it will do this on freeway when driving 70mph, slow down to 65mph and no issue. Although, it seemed to have chugged once this morning when driving 45mph up a hill when during time engine was partially warm

Thanks for your response

 

I haven't checked rotor, caps and wire because it only happens sporadically, do you think?

 

Really..that could be it as well, thanks. Do you think this would be common to stick when it's warm? If in case its the choke this is a can you can purchase that you spray on the carburator..correct?

 

Hi Ken, I’m late on the response although found out that the choke plate does open after being warmed up, is it suppose to open up? I did find that there is no fuel filter, only pump and thinking of putting in a filter and changing fuel pump

 

I would look into a fuel delivery problem.

 

Does this happen all the time or only once in awhile? Is this a 2bb or 4? I had one that the secondaries were worn and would stick intermittently. If you snap the throttle does it go away? If so then check for play In all the linkages where they enter the carb.