I have a 98 Cavalier, 133,000 miles, that the Temperature gauge jumps from midway to cool when it gets up to temperature. It becomes more evident when the I'm going hiway speed. When the temp drops, the car hesitates momentarily and the pitch of the engine sound changes.
I took it to a garage and the mechanic replaced the sending unit. I got it back on Monday and it seemed better at first, but now it's Friday and it's back to the same problem.
Could there be another problem or is something causing the sending unit to go bad?
Other than this, the car runs great
Any ideas...thanks