1986 Mazda RX7 what is wrong with my car?

1986 Mazda RX7 Two Wheel Drive Manual 206500 miles

hi guys, please help me. I recently bought an rx-7 1986, it has 206500 miles on it already now. When I first bought it it was running perfectly fine, the next day since the car was soo dirty I decided to take it to the car wash, the car was that I choose was included with a undercar spray. After the car was washed I stalled the car and when I started it again the rpm would go up but then looses power. The next day I took it to the mechanics, I had a car dianosgtic done and they told me the problem was that the electrical harness was fried up. I asked them about anything else thats wrong with the car and they said that was it. So I paid them $700 to fix the problem, sure enough the problem was gone after I got the car but the next day same problem was happening and the air coolant sign kept coming on all the time even though I had oil change and they put coolant on the engine, the rpm wont go over 3000rpm and it would go up and down. I took the car back to the mechanics and they told me it was the spark plug wires soo I had that replaced for another $60. Then the car was running better this time, but after I got home it started again the same thing and the air coolant lights when it comes on it makes this irritating noise, but it goes on and off whenever. I havent taken it back to the mechanics again yet. Can anyone help me please?
by the way the mechanics said they fixed the electricl wire but they charged 700 for labour but they didnt get any new electrical wires or anything and they told me the wires were fried. Im thinking it could be that the wire pumping the coolant into the engine isnt working or perhaps the fuel filter is not filtering fuel into the engine. But I have no idea I am just guessing. Please help me and thank you.(Also is air coolant the same as coolant?If I buy a new coolant antifreeze for the car is it alright to put it in the coolant container?