Intermitent Surging

[Rtrorkt]

Did a road trip Friday through some of AZ mountains to Willcox. On the way out the car was "surging" when throttle was constant. Seemed to have full power on request, but climbing hills under constant throttle provoked more pronounced surging. Stopped for lunch and when making my final run down AZ 191 surging was gone. After a quick stop I made my way to the track where the "surging" returned.

The balance of the weekend was just short 12 to 15 mile drives to the track, so not a chance to really see if the issue went away.

Made my interstate run back to the Phoenix metro running around 3400 t0 3800 the entire way. No surging, car ran like a train, great trip and did seems to have more power when asked to pass. And to boot the gas mileage was way up. Did 220 miles with just less than a 1/2 tank showing when making the Friday run (up hill for a lot of it) got barely 170 miles from nearly the same amount of gas.

Motor is a bone stock 3.2 in a '69 chassis. Thought about bad gas, but have only used good quality stations, fuel filter is clean. Thoughts?