Doing a tune up for emissions testing two days ago I connected the shop tach meter. It works fine up to 1200 RPM. If I rev the engine a bit more it will come down to 1000-1100, rev it still more and will start bouncing between 1100 and 1400 RPM and when I go over 1500 RPM it will come down to almost zero.
Engine does not miss at any speed. Tested the tach meter on other car and works fine throughout its whole range
What can be wrong? Igniton coil, distributor pick up coil, ECU...? Is any of these three units going south?
Any ideas?
As for emissions today
Rafa

Is this the kind of tach that hooks up to the - of coil, or gets its signal off of a spark plug pickup like a timing light? Make sure you have the right # of cylinders selected.

Pierre
Its the kind that hooks up to negative side of the coil.
It has one function selector with three positions, Volts-Dwell-RPM, one scale for volts. Two scales for RPM and two scales for dwell one for 8 cyl and one for 6 cyl engines. For 4 cyl engines read double the 8 cyl engine reading.

Rafa