Thanks Phil!
Here are some of my responses:

"I really can appreciate your last line of communication." ""I'm learning how much I don't know""

Yeah - it seems there are a lot of things that can cause rough idle... I really should say I'm learning that I don't know as much as my pride thought I did! 🙄

"You did mention the EGR so this engine has one I assume?"

I think I may have added my old engine's EGR to this engine which may not have had one - it's been 3-4 years since I assembled the engine on a stand and I kept thinking I would regret not writing down everything I did... For once I was right on something! 😭

I am 90% certain I did not get the ECU from the donor engine car but I have quite a few old ECUs so I may have one that would work with the old engine... now that it's newly installed in a different car... But first I will find out the stamping on the engine to see what the serial number is and try to figure out how old the engine is.

"Does anything condense on your hand or can you smell the monoxide in abundance when it running?"

I will check that next - the exhaust is pretty smelly - maybe monoxide but I'm not good with smell identification - the exhaust might be a little bit bluish in color but it seems white to me.

"Apparently it is starting to run long enough to get into an operating zone but is it warm enough to be read correctly to the ECU."

How long do you think I should let it idle for it to get in the operating zone?

...

Let me check some of the things you've told me and respond to your other suggestions after that

I'm gonna look for:

air leaks around the intake manifold

Engine age

Condensation on my hands while in the exhaust stream

Spark plug type (NGK but I don't know their heat range?)

ECT sensor type

Thanks for the encouragement Phil!



--
2 1990 Volvo 240s - 1 is my son's sedan the other my 245 in restoration, 1 1999 S70 is my current daily driver until I can get back into the 245!