Follow up from other day, I have attached pics if what I need help with. I put a mk1 1.8 engine into a mk2 1.6 car. And the loom in the pic fits into the speedo plug and it fits into the ECU, but when it comes into the engine bay it doesn't fit into the engine/ injector loom

 

I’m not sure what you want us to say. Just because it plugs in doesn’t mean it’ll work. Pin outs are different, even for identical ECU plugs. Put your old harness or one like it in, or get the mk1 ecu and injector harness.

 

The NA 1.8 uses a ton of different sensors. It uses a mechanical CAS that runs off of the exhaust cam. The 94/95 1.8s don't have a crank sensor. If I remember correctly the coolant sensor on the back of the head is different. So you are going to have to figure out a way to adapt all of those over to the NB sensors. The coolant sensor on the back of the head will be easy, just get the NB unit and plug it in. The CAS and crank sensors on the other hand are going to require more work. I think you can use a NB 1.8 valve cover on a 1.8 NA head if you cut the back of the exhaust cam off.Thats so you can use the NB style CAS, I'm not sure if the NA 1.8 intake cam has the nub that the NB sensor reads though. I think you can just get the bracket that holds the crank angle sensor on and bolt it right up to the NA block if yours doesn't have one but I'm not sure if the NA and NB sensors are the same.The alternator between NAs and NBs are different too. The 1.8 NB alternators are not internally regulated while the NAs are. We never got the 1.6 NBs in the states so I could be 100% wrong about everything and your harness could be using some unobtanium connectors but I doubt it. But yeah there's a bit more work than just swapping a 1.8 into a 1.6 NA. If you still have access to the 1.6 I would take every sensor housing and accessory off of that and see if it will fit into your 1.8 and then figure out solutions for ones that don't work. The general rule with swaps is to use the mechanical stuff off of the new engine with the electrical stuff that matches your car.

Edit, Sorry didn't see your reply Curly... Also what he said haha...

 

That's all I needed to hear, I just posted the pics to give an idea of what I was working with, now I know it is more than a straight swap I can figure out how to go further. I was hoping someone was just gonna say "oh you need this harness" and that would be it. Thanks