Mitsubishi Repair: idle, fuel pump relay, gasket kit

Question
I have a 92 eclipse, 2.0l, turbo, fwd, manual tranny.  

There is a miss in the idle and you can watch the guage and see the rpms rise and fall between about 850 to 1500. those numbers however also seem to fluxuate.

The a/c caused the car to stall out, I tried to run the a/c while cruising on highway, aware it would be hard overall on the car but desperate had a toddler with me and over 100 degrees that day.  The car would even stall out driving 65 mph.

Here's a brief history of what has been done under the hood...
-tune-up= oil&filter, fuel filter, plugs&wires,
-biss adjusted
-timing and balance shaft belts replaced
-rebuilt head,gasket kit, vavles and guides seated and lapped, new rings and bearings
-replaced tps (from a 93 2.0 nt)


anywhere you could direct me would be great.  I'm learning to work on this car myself (being a girl :)  overseen by a 15yr gm tech.  I'm stumped and am needing to keep this car going.

please and THANK YOU!!!

Answer
Tammy,
There are a few probable causes to your problem.

1. You have a electrical problem either in your fuel pump or ignition system.  Since the common items, such as plugs and wires were replaced already, it may be a fuel pump or fuel pump relay issue.  Inspect your fuel pump.  Any Eclipse service manual, like a Haynes or Chilton, provide a testing procedure for that.

2.  Check your Idle Air Control (IAC) motor.  It's located right underneath your throttle body.  The IAC's job is to regulate your RPMs when your car is idling.  When you're idling and the RPMs appear to bounce around, that's commonly referred to as "idle surge"; a clear sign there's a potential problem with the IAC.  Also, turning on the A/C commonly cause a car to stall when idling if the IAC is bad.  Typically, the IAC does not play a part in RPM regulation while the car is in motion (very uncommon for the IAC to be operational when the car is traveling at 65 mph).  But if the IAC is faulty, it can cause stalls at any speed.  Check it and replace it if necessary.

3.  Your car's computer may be malfunctioning.  Read this article for further information:
http://90gsx.com/eclipse/cap/caps.htm

If your ECU is malfunctioning, all sorts of strange problems with starting and stalling can occur.  Inspect your ECU for damage.
Good luck!