Jumpy tach--first time hapenning.

[Projex240]

I get in my car and pull out onto the road---dont get into it at all--but give it a little gas to get to second gear a little quicker. Corner of my eye--the tach jumps--then stops as i let off-then jumps and goes haywire--then stops. I am at a light--and its ok--then i go agin--hit the gas. Same thing. The tach doesnt jump a little upwards and then stop--it jumps and goes nutz for a minute, and THEN quits as long as im out of the gas. Ok--im going to fix this no problem, but i need to know a few things. First--the afc doesnt show any funky rpm readings--so im good where the ecu is concerned, but doesnt the tach work off a signal wire coming out of the transmission, correct? Ill check this and make sure its not frayed or stripped or anything that would cause a funky connection. Also---whgat about the gauge cluster? IS it possible that the cluster itself is going out? Im gong to put a spare one I have in the car this evening, but I wanted to feedback. Can anyone tell me how the tach recieves it signal? I thought it was from the transmission plug that is coupled with the speed sensor, but I alos thought it may be from a plug on the distributor.

Give me some help on the info.

thanks guys,

Josh

[Projex240]

UPDATE--All of this was happening while I was driving from one office to another while at work today. Tonight, when I got home, i saw that the AFC ws reading the correct rpms, and the wiring was intact, and giving me no problems from what i can see. The distributor plugs that would give the tach its signal are connected tightly, and no frayed wires can be seen. When the tach gets to 3300 is when it goes haywire--this could be either When im revving slowly at part throttle, or sitting still and revving hard. Either way, when it hits 3300, it cuts out. Im thinking the tach itself went out and im going to have to replace the cluster. Thats okay--i have a buddy that ahs a spare on, and BONUS, its black. Ive alwasy kinda liked the black faced clusters. Now i get to enjoy getting it fixed and having a new look in the dash.By any chance this doesnt fix it, any other ideas?

-Josh

[ceniack]

ever find out what was causing this, i am having the same problem (i know, i know 2 year old thread)

[480sx]

Check your ground. I was having the same problem, and by moving the ground to a wire that ran to the negitive terminal on the battery it solved the problem.

[ceniack]

what ground were you talking about?

i have tried everything i can think of to fix this problem, and i am still having it..

it sucks

[crash n burn]

we dropped a blacktop in my boy's car, and this happened while we were trying to fire it up. after every start it jumped bakc and forth from 0-9k and back half a dozen times

its all grounds, we ground off the paint where the battery's negative terminal contacts the body. everything was fine, we had to get new plugs, but it fired up on the first try after that