Idles fine but misses/surges at cruise speed?

I took my 440-6 70 Cuda out last night to get gas and it started and idled fine. But,after driving about a mile it started missing/surging. After I got home I replaced the plugs (the old plugs looked fine) and still the same problem. The car starts and revs fine. I put a new fuel pump on the car last summer and wonder if it is bad already. The car gets driven very little. Last time I drove it was last October when I drove it about 50 miles and it ran fine. I'm thinking I'll try replacing the fuel filter next. Any other ideas??

ck the dist + vacumm advance first

Were you able to get a full tank of fresh gas? If so, did it still do it after the fill up?

I did get fresh gas but did not help. I looked in the dist. cap and it looked OK, the car has electronic ignition. Vacuum hose looked OK also. Odd that it starts this after sitting for 8 months, well maybe not so odd .

Something else just occured to me. Normally, I always fill my cars up and put StaBil in them before I store them. Last Fall I put StaBil in my car but did not fill it up and stored it with about 1/4 tank of gas in it. Would water in the gas make it act like this, i.e., idle fine but miss on acceleration and cruise speed??

Had a 77 dodge van that did that. Turns out the gas cap was lose and water would run right in. 1/2 the gas tank was water.

How about under WOT ? ....

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I did get fresh gas but did not help. I looked in the dist. cap and it looked OK, the car has electronic ignition. Vacuum hose looked OK also. Odd that it starts this after sitting for 8 months, well maybe not so odd .

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I ran into this with my Aspen this past week. Ran fine in the fall. Inside the cap looked fine. I decided to put new wires on it. One terminal on the top of the cap was corroded! New cap+rotor plus the wires fixed her right up.