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?

 

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.

 

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.

 

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.

 

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?

 

Thanx for your response guys !

I had my motor replaced last year. Was running fine but now I get the tach
bouncing up, quickly down and then up again and slowly down to a smooth IDLE
at around 850 RPM.

So now I know the shift test I did does not prove anything. Also Canadian
tire just replaced my spark plug wires....the problem happened before they
replaced my wires.

Could it be a vacuum leak somewhere?

 

hey give this link a try

hope it helps


http://www.g2ic.com/tegtips/engine/10.html


fly