Hey guys, I have an 89 f250 with the 460 and C6; the tachometer will jump sometimes, but I won't read most of the time. I've heard about faulty grounding by the coil. Does anyone know what I should look at with this first? Thanks

 

If the engine is not skipping/missing when the tachometer is jumping, the problem is the tach itself not the signal to the coil from the PIP and ICM.