NicericeEL

I recently installed an obd1 ecu with map tune. Everything works great until I reach 5k rpm vtec, then my tac shuts off. I been looking for answers and see that an obd1 dizzy has an rpm wire, than an obd2b does not. There is no rpm wire in my obd2b harness or dizzy. What do I do? I heard the rpm wire carrys the same signal as the crank sensor, but not confirmed. Everything works perfect until I reach vtec.. please help