Mitsubishi Repair: Eclipse Stalling A LOT, speedometer needle, reed switch

Question
I own a '95 Mitsu. Eclipse, 2.0L, GS, manual and it is having some "electrical" problems not sure if they are really electrical or not. I bought the car earlier this year and not soon after purchase did it begin to act up. It likes to die, just shut off, in mid go or at stop light. The car will die anywhere and everywhere. The car has always started right back up with no problem mostly. I have had the car looked at once and they said that they had replaced some wires but could not diagnose the problem. They also told me to wait for it to produce some sort of a larger problem. Well, for me this is a big problem, I am often too afraid to drive my car.  Some days it's fine, other's it's not. Can you tell me what it might be, even if it's a guess I am completly open. Thanks, Vanessa

Answer
Vanessa,
This is a symptom of a broken speed switch, which is a part of the speedometer in the instrument cluster assembly. With the switch inactive, the ECU (the car's computer) does not know the car is moving and doesn't keep the idle high enough to operate the power brakes.

First off, the idle speed for these cars is 750.  When the car is  moving, but the clutch is out, the ECU will keep the idle speed above that (possibly up to 1.5k, if you have ABS).  This is so you have enough vacuum to run your brakes and steering.  So the problem is that your ECU does not notice that the car is in motion.  When you put the clutch in, it tries to take the the idle to 750.  You turn the steering wheel and use the brakes, requiring vacuum and thus
killing the engine.

So how does the ECU get speed info?  There is a "reed switch" that opens and closes whenever a magnet passes by it.  Your speedometer is driven by a magnet shaped like a cross.  As it spins, it drags the speedometer needle with it, to the right, against the pressure of the return spring.  The faster it spins, the more the needle pulls to the right.  It is called something like a "deArsenal" movement, and I might have mucked up the details, but that is how it works.  So Mitsu put this reed switch next to the magnets in your spedometer, and wala!  the ECU now knows your speed.

Two possible causes of your problem.  Your speedometer is unhooked or your reed switch is broken.  Though broken wires to reed switch not likely.

Now this is just a problem I've seen with other Eclipses.  Your problem could be a general tune-up item such as spark plugs, EGR valve, air filter, fuel filter, or even a bad PCV valve.  First, find a different mechanic, because having the engine just die is a big problem.  Have the new mechanic check over the items I mentioned, and hopefully they will find and fix the problem.
Good luck!