Motor runs fine but OD is messing up. Not sure if that has anything to do with this. It seems more electrical than anything. Every so often the check engine, wait to start, trans temp and water in fuel light all blink as the tach goes in and out of operation while the motor is running. Has anyone had this happen before? Any help would be great......thanks guys.

 

is it for your 90? sounds like a crank sensor is bad or a bad connection,but a 90 shouldn't have one I say check for a bad ground or start moving wires around while its running and see if you can duplicate it

 

that would be your throttle position sensor.........it happened to me on my '92

 

sorry its on a 95

 

if it was just the od i would think tps but your other symptoms sounds like the crank sensor

 

Bad engine speed sensor located at the lower pulley or the wiring/connection/gap to it are messed up.