A couple months ago my Auto gauge (ow end Auto Meter) tach started from a steady RPM to periodicaly bounce from the cruise RPM to redline and beyond and back. Eventually the tach quit working all together (fluttered constantly) and I swapped it out for a new Auto Gauge with a shift light in the dial. Hooked it up, it worked fine. Then I went for a long drive, sure enough once the engine was hot the new one started to do the same thing, not too frequently but it did it. I disconnected it to save it.

I have been told it's one of two things.

Cap arcing inside. I have looked, no sign of this, no carbon track. I have looked at night and seen no shorting plug wires either.

Bad module. THe engine runs perfectly, no miss or anything.

It is a stock HEI with a vaccum advance can, non computer controled.

Any suggestions?

Eric

 

replace your ICM....ignition control module...my 1992 Firebird did the same thing also with the stock tach in it, i tried doing the cap thing at first also but nothing once i replaced the module it has worked fine ever since.........