Okay So I'm on my 4th ZX2, so I'm pretty familiar. This has me stumped. 2000 ZX2, 105k 5spd manual, all the goodies available, including pita ABS. Car ran great for 10k when purchasing. Had a plugged heater core. Was summer so I ignored it for the time being. Mistake #1. I replaced timing belt with pulleys, did wires, coil, plugs, all Motorcraft. All back together, car ran flawless for 4k more. On a long drive on a Hot summer day and the last 4 miles of the trip during a downshift the Serp belt started shredding. I made it home with a few cords hanging on and had a spare belt in trunk to swap it. Drove the car back to work and popped the hood. Heard some bubbles in radiator overflow tank. Uh oh, I thought for sure head gasket. I opened the radiator cap (for the first time) after cooled and found a mess of what I can only assume was a sealant added before purchasing. I was going to do a flush during summer anyway for the heater core, so did that with a heater core backflush. Did not have access to a head gasket bubbler, so a compression test yielded no issue, clean oil. So flush done and back to drive. Heater core still not working, tiny bit better but not good at all. Drove it home. Next day all hell started to happen. Three weeks later and a mess of O2 issues and phantom readouts from any tech I could find and I found the problem. Leaking heater core shorted a plug under ECU, power forced into O2 upstream. Took the shorted heavy power wire out of connector, soldered and capped then heat shrink, MAF cleaner and compressed air to the connector and plugged it back in. New O2, new ECU reprogrammed to my car, new heater core. Closed up and voila, car runs good again. Now one issue, sitting at idle the car gets very hot, 228 kind of hot, 180 tstat. Fan kicks on but still it gets to hot. I replaced radiator, same. Got a head gasket bubbler and after 4 tests, cool, hot, whatever I could think. Nothing, fluid stays blue. Antifreeze is clean, oil is clean. It did not get hot before all of this. What happens is two things. #1 - when it gets so hot ,at a stop light when I start to go it has this hesitation and seems mild misfire, never any codes. #2 - when ac or heat related ac settings are used the fan kicks in and the car never gets above 185. However it hesitates and mild misfire with AC on at every take off. It's very annoying and I'm at the point of pulling the head off just because. Something I'd prefer to avoid. Any help or suggestions would be great. New member and hoping I'm in the right place.