The speedometer is ten mph off. It reads 50 when I am doing 40. More importantly, the temperature gauge is wonky. It pegs on hot when I start the engine when cold or warm. It sometimes goes to normal, but not often. I replaced the clock with a tachometer but it too has it's weirdness. It is jumpy at idle and seems to guess at the rpms instead of measuring. It will redline at 40mph or bounce. Oddly, the speedometer will jump when I blow the horn as will the odometer.

The instrument cluster gets its power for most everything through the speedometer's 3-pin L-shaped plug. If you've had the cluster apart for some reason (such as swapping out the clock for a tach) check your work. Otherwise you might want to check for a loose ground at the steering column, and then at the console. Here are the ground locations for a 1990 as a general guide you can compare to the reality of your '91:


--
Art Benstein near Baltimore

Merry Christmas

Makes sense to me. I'll do a ground check. Thanks.