I have a 94 Del Sol, that's plain and simple been through hell before coming into my hands, I've rebuilt the engine once, and replaced the crank since... all within 300 miles of driving it, I just got the crank replaced by a shop (labor warranty and what not this time) and when they fired it up, it has a rough idle, it had one before and I just assumed probably IACV, and just didn't have time to get around to that (or money honestly) the CEL was on so they checked the codes and got a coolant temp too low code as well as IAT low code, shut it off, decided to look at it again the next day to try and see if they missed something. The next day they fired it up, and had no codes, but still a rough idle, so they drove it around and halfway in the CEL came on again, this time it read coolant too temp too high, as well as IAT too high, and a MAP code, and TPS code, as well as a few others (I didn't get a full list, but he told me some of the codes shouldn't even be possible for the car, and I took it to him because I trust him to work on my stuff) our first thought is ECM due to the randomly changing codes, but it never gives me any trouble starting at all, which I would assume it should.... I'm at my wits end and hoping somebody here has either run into this or has some idea as to why it would behave like this.

 

For random problems like that it is often a ground.
Check section 5B in the FAQ: https://honda-tech.com/forums/honda-civic-del-sol-1992-2000-1/faqs-frequently-asked-tech-questions-1998336/

 

The mechanic told me he thought ground, and went through and checked the engine grounds, one was over tightened, but the rest all seemed fine... I don't want to replace the ECM and find out it wasn't the problem, but it's looking like it's either that or over half the sensors in the car went bad... neither of which would surprise me at this point

 

Post the actuall codes, not your description of them. A couple of them you mentioned don't exist.

A possability is some of the sensor plugs are mixed up and connected to the wrong sensors. There are several that use the same style plugs and can easily be mixed up. Verify by using the wire colors for the sensors.