radar502

I never hade this before ,I guessing not uncommon but to me I don't have clue . Just started going nuts after 2,000 RPM .bouncing if get on it a little just goes to way past 6.000 rpm them comes back to wherever it should be .. I read might have bad plug wire ?? NO not it all new and runs too good for that .. Any help .. Thanks .. All the other gauges work fine..