I have a Civic ESi '94. Idle is at 700 around, which should be normal. If I accelerate a little, the idle goes up to 1500, than down to maybe 300 and back to 1500 and stays there. That "going down" to 300 or below let the engine sometimes shut down. What can that be? Its like the engine dont get enough gas for a very short time. The needle is not moving or something. Everything is normal once after a second.