I have a 91 ford escort and about 2yrs ago the motor would turn off while i was driving (around 45 to 60 mph) and the dashboard would light up and the needles would peak. then the motor would turn back on and everthing would be fine. I let a friend take a look at it and he said it was a AC sencor. I did not fix the problem cuz it happened at random and the sencor is about $100. I let the car set for about 3 week and now it will not start. Is it the sencor and if so how do i fix it?

Hmm... hard to say what it is with the info given.

It is unlikely any A/C component is causing the engine to die, but there still may be something wrong with the A/C.

You say the engine would start again... I will assume you don't mean it would start again on its own, without turning the key... because that would just be plain weird.

Two things come to mind.
1. A problem with the timing
2. A vacuum leak.

My guess is bad ignition switch. I doubt the A/C has anything to do with it.

Make sure the fuel pump is coming on for a second or two right after the ignition key is turned on. If it isnt, it could be a bad ignition switch (the electrical part, not the keylock part), or a bad fuel pump relay. However, bad ignition switches are fairly common on Escorts, while the fuel pump relays are pretty reliable.