I think I have two possible problems.I have a 90' 420sel that runs rough when the cruise control is set and also the trans won't up-shift when accelerated hard (fluid level is correct,however its never been changed with 98k miles),and when it DOES shift to the next gear it jerks your teeth out! If I speed up SLOWLY the trans will shift correctly. This just started all-of-sudden like. About a week before that event, I noticed that the engine wouldn't smooth out when the temp reached around 80* cel like it used to when it was warming up (I assume the cold start valve is cutting off at that point). So I thought the thermostat was stuck open because the engine temp woundn't go above about 70* cel, so I replaced it. No help. I still can't seem to get the engine temp up. Could the rough running and trans problem be interlaced with the temp problem? Is there a vacuum relationship between the cruise control unit and the transmisson shifting problem? Does the trans have a vacuum modulator? Vacuum leak maybe? Any help wound be GREATLY appreciated!!