I think its something as simple as soft motor mounts.
Try accelerating hard and backing off a few times on flat ground and see
if you can't reproduce the effect.

Stan Wilder

On Mon, 27 May 2002 17:40:59 -0500 John Rodgers <j_rodgers@CHARTER.NET>
writes:
> When I have a steady foot on the throttle pedal the engine runs
> smooth
> at speed. when I feather the throttle or back off it completely as
> to go
> down a grade the engine bucks slightly, and causes the stick to
> dance
> back and forth (fore and aft acctually). At first I thought somehow
> this
> was related to th Idle Stabilizer Valve, but with the engine warm,
> the
> ECU should have it cut from the circuit. Today, I disconnected the
> O2
> sensor and drove it a bit. Same problem, let off or throttle
> lightly,
> and it does this little buck dance. "It's slight, but it ain't
> right",
> as the Li'l Boy Sez!!! So I don't thinks its the O2 sensor.
>
> I tightened the big crooked hose connected to the ECU in the event
> there
> was a vacuum leak there. Should be no leaks there.
>
> So, do I have a throttle switch problem of some sort. I thought the
> switch shut off the fuel basically, when the foot was taken off the
> gas
> pedal. Is something happening that the injectors are getting
> intermittent fuel?
>
> Anyhow, any suggestions as to how to identify this little problem
> and
> correct it. All comments appreciated.
>
> Thanks,
>
> John Rodgers
> 88 GL Driver
>

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