So I bought my V6 '05 Mustang a month ago, and I noticed a few days later that I seemed to be doing 80mph when it felt I was doing 55ish. Sure enough, I stop and my speedometer reads 25 mph. I cut the
engine off and turn the switch all the way off. I turn the switch back on, it reads 25 mph, I crank the engine and it moves back to 20mpg. I cut the engine off, turn it back on and
after I crank the engine, it moves back another 5 mph. I do this until it moves to 0 and then it's normal. A few days later, for no reason that I can tell, it reads wrong again, maybe only 10 mph over this time, it's erratic. But it always moves up, then after cranking moves down 5 mph.
A few days after I noticed the speedometer doing this, I had my oil changed. A mile down the road from leaving the
oil change place, I see my temp is buried in the red. I pull over, check my
fluids and actual heat and it's still cold (drove less than a mile to the oil change place, then another mile after they changed the oil). I call the Ford place, they say probably bad instrument cluster. I go and test, and sure enough it's the same thing, after I crank the engine, it moves back a little bit. I turn the car off and re-crank it about 8 times and each time it moves back to normal a little bit until it's correct. The other gauges I have saw no problems with, mostly the speedometer but sometimes the temp gauge also.
What is this? Anything I can do? Any help appreciated!!!
Speedo and Temp gauge wrong sometimes? 
