I have a 2008 Solara Convertible, 151k miles, automatic.

I have receipts from previous owner, dealership changed head gasket, they spent like 3k on it. New timing belt and all that.

Oil looks normal as of now, my friend said it smells sweet but to me it does not. 

We got it yesterday, hole in radiator, so I took it out, patched it. And then put back together. Now it's misfiring on 3 cylinders. 

My friend was like, oh the coolant that was left in it, could have had some kind of head gasket stuff.

 And now that's it's been drained, it's [expletive deleted] now.but the coolant that was in it was already half or more than half water, and it was a clear watery pink. That makes no sense to me.

No specific sensor code, just misfire codes. I didn't touch the engine. Just the radiator and I did connect everything back. But one cable, I couldn't figure out where it went and wasn't sure if it was connected in the first place. Was a tiny connector thats connected to the cables for the radiator fan. My friend was like oh that goes to nothing. I'm like ok, I did look as well, couldn't find where it goes.