Jumpy Tach

[GTop]

The tach on my 2001 ETH has always jumped around at idle some. When I was driving the truck yesterday I noticed the tach isn't sweeping smoothly. When I'm on the highway and give it a little throttle the tach is jumpy. This is only occuring under light acceleration. When I'm accelerating hard the tach moves smooth as silk. Kinda like there's a little bit of a bind somewhere. This is a new problem that has never happened before. Anyone have any ideas. Thanks

 

[MCummings]

It's completely electronic.



'98. 5's+ have electronic gauges.



Try this when you are bored. With the ignition switch off press and hold down the trip reset button, and turn the key on, stay holding the button for about 3 - 5 seconds and you will see CHEC in the odometer readout,, then sit back and watch the show.



The tach moves in "Steps". Here's an example, the tach will only move when there is a ~25RPM difference in speed,, so when accelerating slow what you are seeing is the RPM Needle moving up or down in 25RPM steps, so you get a notchy or stop-go-stop-go movement of the Tach,, but when you are speeding up fast the tach doesn't have time to start and stop so it just flows on up in the RPM.



Hope this helps



Merrick Cummings Jr

 

[GTop]

MCummings,



Thank you for the reply. Maybe its something I didn't notice before?From what i've heard the signal is picked up off of the crank. So is the sender at the front or rear of the engine. Just curious. Gotta love all the information you can find out on TDR. Best money spent.

 

[DieselDoghouse]

I think your pickup coil is still on the front of the engine at/near the harmonic balancer. It could be goin' south or out of adjustment, that would explain the twitchiness.