1997 Plymouth Voyager

Hi there,

My problem started today. I started my van and noticed that engine would idle slow then fast and continued to do so until I pulled out. While in reverse it studders and almost stalls. While driving its fine but if I stop at a light it does the studdering and almost stalls. I also noticed that while driving and I went to slow down my speedometer remained at the same speed I was travelling for a couple of seconds even though I considerably slowed down. After about 10 minutes of driving the engine sounds fine and no studdering. When I shut off my vehicle and say go out a few minutes later its fine with none of these problems but if it sits for awhile I experience them.

I would information on what could be the problem, the expense if possible and is it ok to continue to drive it?

Thank you