Okay. I have an all original 84' Subaru GL. It has a 119,000 miles on it, and I am a Nube!

 

The RPM gauge started to get bouncy, regardless if you are at a idle, driving,...it has now bottomed out and doesn't move.

My guesses are it is either the gauge itself, sensor, fuse,...and that is all I can think of.

My question (s):

 

1. Does my theories sound close?

2. If so, how do I check for it, and how do I fix it.

3....and are there parts available?

 

Thank you in advance for any help that you can provide. 

Here's a quote with an explanation...

 

 

ahh, the classic jittery tach.

What's happening (I'm betting) is that the lower spinning bits in the distributor are occasionally hitting the sides of the distributor body. How does this happen? Glad you asked!

The distributor shaft has some flutes machined into it that draw a small amount of oil up to where the distributor shaft rests the distributor body. Unfortunately the shaft does not ride on bearings, but just sits on thin washers. Anyway, the flutes can get clogged, eliminating any lubrication of the washers, and the distributor shaft assembly eventually wears it's way lower and lower in the housing, eventually hitting the sides of the housing (why this makes the tach jump, I don't know, but it does).

 

You can get a set of "distributor thrust washers" from a Subaru dealership for a few bucks and add them to the stack to raise the shaft assembly (add some grease while you're there). You'll have to tweak the timing a bit too. If not fixed it will get worse, but at a very slow rate. I drove mine for six or seven years with a jumping tach.

If you get a distributor assembly from a wrecker, you'd be wise to take the lower gear off, remove the shaft, and make sure the lubrication flutes are clean.

What he said

Here's a quote with an explanation...

 

 

Wow from 2004 as well. You get a gold star for digging that up

Thank you everyone. That clears it up a bit. I guess I will move towards getting the parts.

 

On a side note. My son was driving to school and called and told me that the tach started to work when he turned on the heating fan? I am sure it is all part of what Scoobydo said.

 

Again, thank your for all of your reply's.

I would check the play in the distributor shaft before ordering parts as it sounds to me like you have a gauge issue or electrical problem. If there's no lateral play (back and forth) in the shaft, then that's not your problem. A SMALL amount of play is normal. More than slight movement is not.

Thanks again to everyone. Now I just need to find the time to do it.