Is my tach sensor the culprit?
 

I searched, couldn't find anything relating to my specific problem. When my truck is cold, the tach doesn't work at all. After about 5 minutes of driving it begins to function, how accurately it functions is a mystery. The idle speed it shows is usually different every time I stop. When I use the turn signals, the tach needle bounces(2-300rpm) in sync with the blinker. Could this be the sensor or a cluster issue?

Sounds like a dash connection problem to me for the most part because of the blinker induced bounce.

I just replaced my tach sensor, and the tach was doing all kinds of weird things like you described (IIRC - even blinker bounce). Got any spare parts, or temporary access to another tach sensor ?

Not yet, it's my first diesel and I've only had it a few days. Haven't aquired any spare parts yet.

Sounds like the sensor is going. Ford only part and about $60 or so, E5TZ-17B384-A TACH SENSOR

Mine only works when you rev the engine. At idle and when coasting it reads zero. Where is this sensor anyways? I'd like to look into replacing it.

Tach Sensor Location

-Enjoy
fh : )_~

Awesome! Thanks! I think I'll just throw a new one in while I've got the motor out. Does that sensor have anything to do with how the PCM controlls the E4OD or is it a sending unit only?

It controls quite a bit. Without the sensor, the trans won't work correctly (as well as the TPS/FIPL, speedo drive, brake lights and gear selector). That's one of the reasons I went with a Baumann controller, less inputs to scramble the trans.

So the tach sensor could be causing my eratic tach operation and messing with the shifting? Are there any other variables to check?

That would cover both of those. You could check the grounds and connections for both, as that would also make it look like a falied component. I still vote for the sensor, they seem to go out after a few years (maybe 20?) of use.

ok i have a question my tach works when i am cranking it bouces but thats it when it starts it dosnt work at all could that be the sensor?

Usually before the sensor fails the the insulation will be cracking and showing bare wires right as they come out of the sensor. If they are it is a sure thing the sensor will not be long for this world.

I just noticed that last night on my sensor. The wire is bare for about 2" coming out of the sensor. Guess I will look for a new one.

If it's still working, apply a little sillycone (silicone) around where the wires enter it to prevent moister from getting in and shorting it out. They are like something like 50 or 60 bux!

Yea, I know, I would replace it to! :)

-Enjoy
fh : )_~