OK, while playing around with the ignition / idle system of 6530 I noted something very interesting. As I previous stated, the tachometer makes small jumps upward, intermittently. I accidentally touched the wire that goes to the negative side of the ignition coil primary circuit (color WS) and noted that I was getting intermittent shocks. These shocks were at the same time that the tach jumped! When I connected a small neon bulb (i.e., an NE-2 for you engineering types), the bulb would blink intermittently along with the jumping of the tach. (Hey I got fed up with getting jolted so I substituted the bulb instead.) Remember that the engine RPM is NOT jumping only the tach is. I suppose the tach is getting these voltage spikes and that is why it is jumping and maybe these spikes are affecting the idle ECU controller. The spike occur only at low RPM up to about 1400 rpm. Does anyone have a clue as to what to do next? Dave & 6530 thank you... [Non-text portions of this message have been removed]