85 380 se idle only miss

[jimandsuzy]

My 380 misses until I pass about 1300 rpm then is smooth until the speed gets below 1300. It acts the same whether I pull away slowly or speed off. The miss is constant and seems to be one cylinder. It started out missing for about 10 seconds after a cold start (70F or so). Plugs were changed and then soon after this miss below 1300 rpm started and has not varied for about 5000 miles now. The distributor cap is clean. I don't know if it could be a fuel or ignition problem and can not start changing parts ($) to try to find the problem. Car has 186,000 miles and I've had it about 7,000. Thanks for any advice.