would a tps sensor be the reason? the speedometer is also hopping?
Yes, or no.
Unless you tell us the year and engine/transmission combination of this vehicle, that’s as good an answer as anyone can give you.
Pontiac made the Grand Prix for a long time. They’re not all the same.
Then there’s all that other info people would need.
Like under what conditions this kind of thing occurs. The mileage would be nice. Some info about maintenance history (plugs, wires, filters etc.) would be nice. If the check engine light is on or not…
Call your doctor tomorrow. When someone answers say “sneezing and coughing. would a cold be the reason?” See how far you get. (They might just hang up on you for being rude).
my apologies… I thought that the site would give that info since I typed in this… 2000 Grand Prix w/ 3.1 SFI… Day two of my investigation of this is indicating a speed sensor now. Car is in the shop having a diagnostic scan done and hopefully this is the culprit. The original problems were speratic gear changing and speedometer hopping.