Factory Tach malfunction at idle

[rewbrooks50]

The tach drops to zero when I let off the accelerator and at idle. And the E4OD warning starts flashing.

1994 F350, dually 7.3 IDIT.

What's the problem?

 

[Philip1]

Your issue is likely the tach sensor. Either the sensor is bad or the face of it is dirty

 

[rewbrooks50]

found this thread: https://www.oilburners.net/threads/tach.57342/

I will see if I can tract it down.

Thanks

 

[renjaminfrankln]

I had the same issue. New sensor and it is much better, but still occasionally drops to zero at idle. Sensor was whatever I found on rock auto.. not OEM, that could be the problem.