While driving along at about 45 MPH (about 1500 rpm) with the tranny in 4th and torque converter locked up, the engine may start missing randomly if I apply a little throttle (but not enough throttle to disengage the lock-up). It seems to happen more if the weather is wet and cold. Also this is after the engine is completely up to temperature.

It doesn’t feel like an injector miss since it is such an instantaneous miss fire. It feels more like an ignition problem. As my speed increases the miss fire goes away. It also goes away if I disengage the lock-up feature probably because the RPM increases about 800 RPM if the torque converted is not locked.

It could be a bad plug but I kinda doubt it since they were replaced not too long ago and because the engine missed before the new plugs went in.

Could it be that one of the coils is breaking down? I wonder how I would diagnose this problem since it only happens under load. I would need to have the car on some kind of dyno to simulate the load.

Any suggestions or experience with this?