i have a 91 civic hatch

and sometimes when it gets really hot out side and im on a complete stop the tempeture gauge starts to rise up and when i start moving it goes back down what could it be?

also sometimes when i come to a complete stop it feels like it loses power and it feels like its going to turn off on me and some times it does shut down on me what could it be?

 

Most likely headgasket. You need to check your cooling system, autozone loans the pump to see if your car holds pressure