92 Integra GS - Tachometer bounce up and down repeatedly

I can now reproduce this problem consistently. Engine warm and i'm in Park with consistent 850 RPM idle. I then would just move my shift stick (it's
an automatic), just very slightly down (towards R but not in Reverse yet) and hold it there and my tachometer would start bouncing up and down repeatedly.
What could be causing this? Something loose in the distributor?
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If you've tied it conclusively to moving the transmission shift lever,then why suspect the distributor? How would moving the shift lever affect the distributor? (or the idle speed?) Perhaps there's some switch on the shift lever that's intermittent.
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Jim Yanik
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Thanx for your response Jim.
I forgot to mention that the tachometer bounces when I'm drivinng and then come to a stop. It bounces down once and then up again.... That is why I said it could be the distributor because it happens without moving the shift stick as well.....but I'm not really sure.

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Consider that the engine/transmission pair is mounted so it can -move-(WRT the car body;motor mounts),and the shift linkage then goes to the shifter,thus Opportunity for the shift lever to move when driving.
Or you could replace the igniter,which provides the signal to the ECU for the tach.(or scope it's tach output if you have the tools)
www.tegger.com has some good data on the igniter.
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Jim Yanik
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You're fooling the computer! You're manipulating the lever so as to cause intermittent contact with the microswitch that tells the computer whether you're in neutral or reverse. Don't do that. It tells you nothing at all.
As far as your tach bouncing when you come to a stop, that's because your tranny is downshifting back into first.
How long have you owned this car?
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TeGGeR

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hey give this link a try
hope it helps
http://www.g2ic.com/tegtips/engine/10.html
fly
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