If I mash the gas or hit a hard bump my temp guage will drop then eventually come back to normal.

Heat works fine and the cooling system is topped off and not leaking.

Is this a bad coolant temp sensor?

Thanks!

 

Bad guage imo?

Terminals/wiring bad?

 

I'm thinking you may have wiring issue, loose connection, probably at the engine. Check your engine mounts and make sure that the engine isn't bouncing around.

 

The wire on my temp sending unit was loose, caused this same problem. It's located on the passenger-side of the engine, follow the upper radiator hose and you should find it.

 

i had the same thing with my GXE cluster, tach would do nothing or thrash 3/4 of the time, and the temp gauge would work half the time and the other half just shoot up to H or limp at C, try swapping clusters