1992 Camry Cold Start Up Problem

[Mark1952]

I Need Help,
I have a 1992 Toyota Camry, 4 Cylindar, 2.2 engine. I have 171 thousand miles and the engine sounds like a pussy cat. Here is the problem and what I did so far:
When I first start it up in the morning i let it warm up before taking off. When I start driving and I come to the first traffic light, as I'm slowing down the cars starts shaking. While this is happening I glance at the rpm's gauge and the red needle is dropping to near zero (0). I immediately put the car into neutral and give it some gas. After doing that once or twice the problem goes away. This is a intermediate problem. In other words it does not happen often.
Yesterday at the repair shop they put a scanner on the car. They changed the coolant temperature sensor and he also changed the gas filter because he said it looked very old and rusty.
This morning I got into the car, started it up and I let it warm up. As I was coming to my first stop it started shaking again. When I looked at the rpm's gauge it was dropping towards zero (0). This time I did not put it into neutral, instead i waited to see what would happen. It stalled out and I had a big smell of gas. I re-started the car and it is normal now.
What is going on or happening? What could it be. I need an answer that I can take to the repair shop.

Thanks,

Mark