Misfiring under 2500 RPMs, 1.7L Misfires, but only under 2500RPMs Options

[jackr67]

90% of the time, my 1.7L injected car runs fine.

Ocassionally and very abruptly it'll drop two cylinders under 2500 RPMs and pick up a very low idle, no doubt due to the miss. It doesn't seem to be localized to any one cylinder - I've pulled each plug wire one at a time and they all affect the idle about the same. Above 2500 (to 3000 RPMs, in between really) it runs just fine. It goes from a debilitating miss to full power very suddenly as you coax the RPMs up. Usually if it picks up this problem while driving it'll last the rest of the drive, but then be fine next time it's started, though sometimes it'll self-correct after a couple minutes.

It's been suggested that the advance plates in the distributor may be sticking, otherwise I'm not sure what else may be causing this. This behavior used to be rare but now is ocurring quite a lot more often.

Any thoughts before I dig into it tonite?

Thanks!