Hyundai-tech: after changing cam shaft sensor, car kicks back before stopping

Hi,
I have Sonata 99 GLS (V6) and recently replaced cam shaft sensor at a Hyundai-dealer in Cleveland.
I am having a strange thing. It does not happen all the times.
Sometimes, the engine revs up all of sudden (about 200 rpm more) and the increased RPM does not settle down. When this happens, the car kicks back right before stopping. It's like a hiccup or slamming brake pedal hard (of course I didn't slam the brake pedal).
The only way to make it go is to turn the engine off. On restarting the engine, the car runs good.
I've made appointment with the service as they have warranty back up on their service.
However, I want to know what is really going on here.
Is the newly installed cam shaft sensor mal-functioning?
I have replaced the timing belt about six months ago. If the timing belt is off by a tooth or two and causing this problem, it should happen all the times, I guess.
Any suggestions or explanations on this issue is highly appreciated. I want to fix this problem.
Thanks!
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It sounds like there a throttle position sensor issue. If it's reading too high, the car won't idle down, and the transmission will shift hard when coming to a stop because the TCM thinks you've got your foot on the gas.
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There is no check engine sign on. If it is a throttle position sensor issue, do I need to replace the sensor? Or, is it just matter of setting the throttle sensor?
hyundaitech wrote:

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After looking in the shop manual, it appears this sensor is adjustable, so it's possible it's an adjustment issue.
Ideally, when the car isn't idling correctly, you'd check the throttle position sensor (TPS) reading. Unfortunately, a scan tool is the easiest way to do this. The scan tool reports a data value of on or off for the idle state. If you've got your foot of the gas and the idle switch reading is anything but "on," then the TPS reading is the issue.
Then you'll need to figure out what the issue with the TPS reading is. Make sure there is slack in the throttle cable. It's possible it's an adjustment issue, but I really think neither of the above are likely to be the cause just because you say the problem is intermittent. I suspect the throttle sensor itself is defective or there's poor contact in the throttle position sensor connector.
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