I know that I fixed an identical issue to yours on a chevy cavalier by replacing the spark plugs.... it was sputtering and idling poorly (and stalling occassionally) with the new plugs it idles smoooth and has better power. The old plugs were charred and shot.

If your plugs are old it might be worth a try. Could also be the distributor, spark cables, or the rotor/coil.

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