318 Running Strange in 75 Cordoba

[76mopar]

Had the same problem with my 2 Dobas turned out the gas tank has a pin hole in the top side and the tank was full of rust. Also had it act funny on my Charger when the automatic choke messed up. Could be a number of things.
If you think its rust or junk in the tank I would put on one of those universal clear tube fuel filters so you can see what color the fuel is as it passes. Thats the only thing that helped me figure out my problems with the rust in the tanks. Thought it was sludge until I put a magnet to it.

 

[Lets Roll]

Sometimes if there is enough garbage and stuff in the tank it can do this and then it settles down after the engine is off and then it happens again as it pumps it back up. It can also happen again after the filter is replaced if the tank isn't cleaned out.

 

[71newp]

Car has 34000 original miles.

Starts and idles very well, very smoothly. Drives well for a little while .... then it starts to act like the timing is off. It loses acceleration, spits and sputters, and eventually quits running. Once the condition starts it is very difficult to keep it running. One time I was able to get it to come out of the condition by keeping the RPMs up until it went away. However; I usually have to let it die then wait about 5 minutes before I can start it up again.

I had a very similar problem, except my '76 360 would run rough at first, then great for 5 or so minutes then awful and die. I changed the coil and voltage regulator and it got a little better. Then I changed the Ignition control mod and after it warms up it runs GREAT! My new ICM was around $25 from rockauto. Good Luck!