My 87 has an in dash tach and at times it jumps around. It seems to jump up in rpm like something electrical is going on with it. Anyone know what might cause this? Thanks

bad ign wires!! Take a spray bottle and mix a little salt in with water and spray on wires. This will show a leaky wire.

I had this happen all the time on my 87 z28. I turned out to be my pickup coil in the distributor. It normally wouldn't happen when the vehicle was first started. But after driving it for a while it would do it (inconsistenly I may add). It wasn't a "every time I drive" occurrence. Drove me nuts!!

JDC

hi
i have the same problem
what is a pick up coil

The P/U coil is inside the distributor you have to remove the distributor and disassemble it to replace coil it where your points use to be

there is a question just like this in the MSD ignition search then go to popular hotrodding articles they have what everyone said and little more