My 92 LeSabre 3.8 will only start misfiring/hesitating after getting hot (30+ miles) and then shutting off the engine for a short period of time. The first time, I replaced fuel filter, plugs and wires and drove it 180 miles without stopping and it never acted up). I've had it occur several times since then. And last night after getting the problem started, I replaced with an entirely different set of coils and the same problem...non-rhythmical misfires (more so at higher speeds 40+) every few seconds or so.
I just found the site for the service Engine Soon Diagnosis (
http://www.geocities.com/dann8785/se...nginesoon.html) and will get the engine hot again and look at the code that has been displaying (but I was unaware of what it meant!).
I 've checked into the LeSabre forum but have not seen a close match.