Tachometer question

[sumpinsfishie]

I browse through the post here QUITE often , but this is my first post. I greatly appreciate any and all information that i have recieved from this place. There is obviously a lot of knowledge here. There is 1 thing that I am having trouble with that i dont understand and I cant get any good info from anywhere. My problem is that while driving, my tach works great, but when i give it excessive throttle to the point that it kicks down, my tach drops to zero. I have put the transmission in 1st gear (auto tranny) and slowly accelerated and it does the same once it gets to aprx 2100-2200. I have searched for scematics or wiring diagrams all over and i cant find any. I really cant find any info on how to troubleshoot this problem. i would appreciate any info on how to troubleshoot and/or where to get diagrams to use for future uses. Thank you for taking the time to read and consider my issue

 

[sumpinsfishie]

By the way, ANY info will be useful. I'm not even sure how or where it gets its signal. From what i have read, it seems that it comes from the PCM, but even before that, where does the signal orginate from? The coil, the CKP??

 

[rileyrs]

do you really need the tach?

either way, the rangers tach used to stick, i didnt know why, but after an oil change, it worked better, still sticks sometime but less.

i didnt even expect it to do anything, it was just changing the oil when scheduled, but it turned out to help.

other than that, idk what to say

good luck