It sound like something has gone wrong with the PCM. A couple of things may be causing it, one is the crank sensor and the other is either of the O2 sensors. The usual failure mode is the PCM will not do anything when one of these shorts out. What you have sounds like a partial failure. Does the check engine light come on for 3 seconds when you turn the switch to the on position? If not, the PCM is definitely malfunctioning.
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