Tonight my ISSPRO EGT gauge started jumping around. When coasting it will go from 300* down to 100* until I give it more fuel. If I step on it hard it goes up like normal. It has been installed for a couple of months w/o any problems. Any suggestions on things to check?

 

Loose wire either a hot or ground wire. I had the same problem.

 

Wasn't my egt gauge, but your symprons were the same I was having with my tranny temp gauge. Checked all wires and even reconnected to another source, still same problem. New amp took care of it. Call Isspro, no hassle support. Got it in 3 days.