bouncing tach dilemma
 

hey guys,
i have an '85 GSL-SE and lately the tach has been bouncing around from idle up to 6500rpm. it changes and sometimes stops when i put a load on it, as in press the brake or turn on headlights. i have swapped out the coil and also the cap and rotor. i've even swapped the leading and trailing coil plug wires(racing beat wires) to the distributor and no luck.

it started after i had a problem with the car starting which was the factory aluminum wiring and the battery terminal. one of the guys at work pulled some slack out of the positive wire and put a new terminal on it and thats when it started. he has tried to move some of the wiring to fix it and as stated before, i've swapped out the coil and cap/rotor and cannot come up with anything. i would like to resolve this w/out having to swap out the tach. its getting the signal to bounce around somehow. or maybe its just fried and i have to replace it.

any helpful ideas?

Sounds like a failing trailing ignitor to me.

i'll try that tomorrow. thanks for the response

I had a bouncing tach that I couldnt figure out FOREVER. I, like you, tried replacing everything under the sun and nothing worked. I even tried DLIDFIS. It finally just went away on its own, but it happened after I got new plugs. Related? You tell me...

~T.J.

I've seen two FB's do this periodically. One was a mint car...pretty nice. I think there's something in the guage cluster that works it's way loose of something over time. If it were a coil I would think you'd notice a diffeence in performance.

My FB was only a couple years old and had hardly any miles when I bought it and the tach has always bounced. I never have figured it out. I know it wasn't the ingnitors because I replaced them. I agree with Makenzie71. I think it's probably the tach itself that has a problem. Eventhough the tach bounced the engine always ran very smooth.

Anything related to the trailing ignition. Good time to clean off the spade connector to your coil.

inittab is right. The tach gets it's signal from the trailing coil so your answer very likely lies there.

F-

I've noticed that mine does it when it starts to get cold. I just figure something in the gauge cluster is just old and the cold is have a negative effect on it

the connections on the coils have already been done.

didn't work. i haven't tried the ignitor yet. i was supposed to today but drove my FD to work. taking the SE tomorrow....well, today

bag igniter or faulty tach, I have seen this in older ones and it was a faulty tach