I am having a problem with an erratcally recurring error code 8 (TDC sensor) on my 89 Legend.

The engine is running extremely well and it has just passed emissions. Nonetheless periodically the error will come on, and if I clear it, it does not reappear.

I have checked the sensor line, it indicates 869 ohms (ok according to the manual) and no short to ground.

Eventually (days later) it reappears, after I have driven sustained highway driving and parked for about 10 minutes (if I park for a longer time it does not reappear.)

I am not convinced the sensor itself is actually bad, before I go to the expense of replacing it I would like some way to be convinced that it is indeed the sensor.

Any comments or other suggestions as to what could cause this?

j