I had the same symptoms and I found no loose grounds. My mechanic thought that it might have been the SI Board, so it was replaced under warranty (CCU Uptime). They had a small disclaimer in the literature with the newer ECU unit that the conductor plate can cause the temp gauge to be inaccurate. What does a conductor plate look like and where is it? GOOD QUESTIONS! Haven't even looked in the Bentley manual for it since it was taken care of by the mechanic. I do know that the fix was only $90 or so for the part/labor. Not bad considering the cost of a new SI Board. Hope that helps! Chris '85 e24