I have a '82 242 w/265,000 miles. For the past few months the car has been idling roughly. I usually let the car warm-up for a while, for about 3-4 minutes, before hitting the road. If I don't it doesn't like it and runs poorly. So while sitting in the car waiting for the temp to get up, I have begun listening to the engine. For the first minute after starting it runs nice and smooth. However, as it gets warmer I hear the engine start to rev down, almost to a stall. Just before it stalls, something will catch (what I don't know) and the engine will save itself from stalling. This cycle continues until I get bored with sitting there and I take off. Why is the engine cycling down almost to a stall and then catching itself? This hasn't been a problem really, except more and more frequently the engine is not catching, and is stalling. Then I have to wait a minute or so before it starts up again.

In the past 3 years it has had a new warmup regulator, several fuel pump relays, 0xygen sensor, ignition pins, and six years ago a new wiring harness.
Don't know much about cars, so this could be something obvious. Any ideas?

GRC