maverick

So my 91 has an interesting issue. The rev counter works fine at idle...give it throttle input and it goes to zero.....while driving if you’re on the gas its at zero, coast and it jumps to current rpm. Any additional throttle input and it goes to zero.... any ideas?

Scott Dunavant

Your EZ69 signals the Interface Relay VDO behind the Fuel gauge. That signals the Speed Sender tach. The Wires do run over to your diagnosis plug.
Plug also leads into the 965 VDO brain Central Informer. Also Try grounding point behind the VDO Relay behind the Gas Gauge. Ground point under driver's seat. Ground point in engine compartment on left upper side. Clean and tighten ground points. Relay is the cheapest. Swap tach with 964 is also simple.

fritz k.

Agree with Scott, most likely a ground failure.

Fritz

maverick

Many thanks for the input, I’ll check the grounds. Also my stock EZ69 died and I was able to get a replacement from Cobalt that was an ex Brumos race unit. We don’t know much about the unit but the tach was working with it initially.

Metal Guru

Make sure your ignition coil is not failing. When it goes bad, it will kill your EZ.

maverick

Well that sounds ominous Paul.....are there any specific test to determine the health of th ignition coil? Also I’ve seen images of a traditional coil, long cylinder and also a small square coil.....which one is applicable to the turbos?

heliolps2

Happy Holidays,
The small square coil is the right one for your 965

Scott Dunavant

The coil is the cheapest. You could buy one on EBAY for $100 if that doesn't fix it I'll buy it from you. It's under the intercooler. Mine is original.