93 300E error code 7
My 93 300E2.8 has developed a bad stumble/misfire at idle and when initially accelerating. At speed, it seems fine, has plenty of power and does not miss. The check engine light is not on but when looking at the codes at the connector underneath the hood, I get a "7" which I think means ignition failure. Plugs were changed about 2000 miles ago (ran fine until about 50 miles ago) and looking at a plug I took out, it seemed fine. What would be the things to look at for this problem?