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I have a 2001 Civic DX, Auto, ~127K, good overall condition. For the past year or so, it has been "kicking" or so on and off. For the past few months it hasnt been bad. But, just recently it has started up again pretty regularly.

What happens is: sometimes when I am doing roughly 35mph, at a certain point at which I press the gas pedal, the car starts "bucking." If I press the gas harder, it stops. If let go of the gas pedal just a LITTLE bit, it decelerates more rapidly than normal, and the throttle doesnt maintain what the speed should be at the level at which I am pressing the gas.
ALSO, when I am on the interstate doing roughly 60 mph, it is as though I am at that same threshold, but the car doesnt kick as bad. If I press the gas harder it stops, but if I release the gas pedal JUST A LITTLE BIT, it decelerates quicker than normal and doesnt maintain constant speed.

I went to Auto Zone to get the free diagnostic exam about a month ago, it said it could be the O2 sensor and/or some ignitor coil. Feeling that their machine probably wasnt very reliable, I pushed it off and the problem stopped (or lessened) for a while.

I had thought maybe the TPS, but the car doesnt idle rough, but it does idle a little low sometimes.

Maybe this is a Transmission problem. Anyone familiar with this issue?

Any clues?