My a/c compressor in my 1998 mitsubishi eclipse in seizing up and sticking causing my engine to lose power and cut off in drive and idle

Could be many things. You may be noticing the loss of power, when the compressor is on. However, you could have a fuel issue. Such as, dirty fuel filter, or bad fuel pump. I believe the fuel filter is also part of the fuel pump assembly on that car. Good luck.

the rise in idle at startup and then a slowdown indicates possibly a throttle position sensor, sticking choke or a vacum leak. the TPS and choke is something that will have to be checked by a tech, the vacum leak can be found by starting the car and sticking your head under the hood and listen for a hissing noise that sounds like air escaping somewhere......if you can find it, and put your hand or fingers over the leak, the idle should rise and then you'll know that's your problem. this is entirely possible due to the age of the car, the number of miles on it and the fact that most of the vacum attachments usually use rubber hoses which will deteriorate over time and cause these types of problems

Possible sticking egr valve

have an ac specialist check the gas pressures and the compressor as it is drawing too much power from the engine or too much power from the ignition circuit
I would suggest a compression test in the engine as well to get the engine condition. Most ac compressors take about 5hp to drive and if the engine is a bit sad then that is too much power overall.

Try this.

This problem is commonly caused by a dirty automatic idle speed control valve and throttle valve. Buy a can of throttle valve cleaner (do not use carburetor spray cleaner!) from NAPA or Carquest (made by CRC chemicals) and spray it into the air intake while the engine is running, use up about 1/2 the can, engine will try to stall hold the speed up, shut it down and let it soak for 30 minutes, restart and blow out the remaining fluid, shut it down and disconnect the negative battery cable for 5 Min's to reset the base idle control

it's either your losing pressure in your head... check your vacuum... it's causing no pressure in your engine which its losing power causing the belts to idle out of tune..

Have you changed the spark plugs and fuel filter yet?

This may been an ignition module or a MAF sensor, this car may need to be diagnosed using a OBD I computer code reader to accurately diagnose the problem.

check for vacuum leaks in failing hoses and loose fittings

Does your engine temperature guage read normal? Have you checked your coolant level? This can be the result of a partially seized thermostat... there is also a valve in the heater core lines that can seize partially closed. As the engine speed increases, the water pump can force more water through the partially closed component.