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Guest Message by DevFuse

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Jumpy tac at higher revs

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5 replies to this topic

#1 gvh


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Posted 11 March 2004 - 11:18 PM

On my 83 e81 I had tracked down a serious problem to a bad distributor. Back when it went wrong the tac would dance then peg just before the engine died.

After I replaced the distributor she runs pretty well and that problem went away. Now she runs a little rough and at about 2500 rpm the tac will jump an 1/8" or so every one in awhile. It isn't a natural engine kind of jump, it is a twitch. Really fast then gone.

I have swapped spark plugs, cables, coil, cap and rotor. Timed and reidled. Took her for emmisions and she failed by just a bit on hydrocarbons.

The tac has me thinking it is electrical but for now I am having a beer, taking a break and looking for ideas.


#2 subiemech85



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  • down by the river

Posted 11 March 2004 - 11:35 PM

bad wires or moduole

#3 GeneralDisorder


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Posted 12 March 2004 - 01:22 AM

Distributor shaft bushings - always is. There's shops that can rebush them for you - here's the place I use:


Cheaper than a new disty, and as good as new - used is only buying time, and generally costs about as much as having the bushing done....

It is NOT the module. In fact, I have never seen a module die in one of these...


#4 Sweet82


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Posted 12 March 2004 - 11:08 AM

My tach has jumped for several years now.

I have never fixed it

Maybe I should but so far it hasn't been a problem.

82 Summer, jumpy tach
01 Forester, regular tach

#5 GeneralDisorder


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Posted 12 March 2004 - 03:59 PM

When it gets really bad, you'll start to lose power, and the rotor on the shaft will smack the stator, and chew it down. Not good.


#6 Carter


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Posted 12 March 2004 - 08:16 PM

Then when the bushings get really bad, the tach will skip all the way down to zero before returning to your operating speed. It will do this for awhile until it goes down to zero and stays there. Nothing will get you going again except another distributor or fixing the bushings.

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