I have a problem where my '76 280z throttle sticks. I drive and go above 3000 rpm and put the car in neutral and it stays at 3000. If a tap the accelerator it will go down to idle or about 1500 rpm, if sticks at 1500 rpm, I tap it again and it goes down to idle about 750 rpm. This also happens while driving if I am above 2000 to 3000 rpm and keep the car in gear it acts like cruise control it continues at the same rpms, until I put into nuetral and tap or tap while still in gear. What can I do to fix this??