Okay, here is more detail along with what I think happened.
Its a new build. Not flown yet. Another point is that it is a used engine that was removed from a Mooney along with all FW fwd accessories. I have no clue of how they cared for the engine prior to my purchase other than what they told me and what the logbooks showed. It had the appearance of cleanliness, but.......Also, after some contemplation I did have the engine torn down and sent the crank off for inspection as it was purchased as a low time engine with a "light" prop strike. I chose to do this after purchasing even though an A&P signed off the engine with proper ADs (accessory case gears replaced, etc) and airworthy, the crank was only mic'd for runout. In other words, I'm thinking that its also possible things got contaminated in sloppy handling at some point. Wouldn't have happened with me doing it myself but other hands handled this engine before me and it may have been handled by someone, in a bad mood, on a Monday, whose favorite grandma got run over by a reindeer, and he had dirty hands. I really don't have any way of knowing.
I explained earlier that a hose was made by a mechanic at the airport. Additionally, the mechanic installed the hose for me as I didn't mention that earlier (I don't like to point fingers). The hose is located where there is no filter before the flow divider. I feel that debris was not cleared completely from the hose and then the hose was installed and got rubber debris/cuttings into the system. I've now pumped several gallons of AvGas through the system and got no more contamination. Likewise, I disassembled and verified no more contamination visually both at flow divider and injector nozzles.
I suspect the debris made its way into the flow divider at first startup and has been sitting there up until now. The debris finally made its way to the injector nozzle and plugged it after then engine was run a little more. Enough fuel was passing thru the plugged nozzle for the engine to develop CHT and EGT at idle. When the throttle was advanced, no additional fuel could flow and the cylinder could not keep up thus went cold until the throttle was closed back to idle. I also noticed a slight rise in idle RPMs. I'm not an engine expert by any means but that is my diagnosis.
After cleaning everything up, I started engine and it is now running better than it ever has. When the engine was started for the first time, we fought lean/rich mixture issues and general roughness for several days before getting things running to what I thought was supposed to be normal/acceptable. At that, the mixture seemed to be high maintenance at various throttle settings but others who had injected engines told me it was pretty normal for our altitude (3600'). I've never flown behind an injected engine so okay, guess they are higher maintenance to run....I could build full power etc, but just had to be on the mixture right behind the throttle to keep things running well.
Since cleaning and running afterwards, the mixture now acts MUCH more to what I am accustomed. The cylinder temps are more even along with EGTs much more than what I thought was normal for my engine. Thus, this supports my theory that the debris set in my flow divider since first startup and was affecting even flow to the injector nozzles causing EGTs and CHTs that were more uneven. I would never have opened up the flow divider had a nozzle not plugged up. I'm glad I did!
Lessons Learned (Again, I'm no expert but I am learning!)
1) Don't trust cleanliness of any fuel system hoses until you inspect them with your own eyes. Keep them clean and install them yourself. I trusted that the guy who built my hose verified cleanliness. I'm not positive that I would have been able to catch the debris visually but I can admit that I didn't check for it which is not a good thing.
2) It would be beneficial, to pump a gallon or two of fuel through the system up to the end of the hose prior to the flow divider and prior to first run. After that, hook things up to the flow divider. You have a much better quality benchmark of how things were done and where they stand.
3) Don't be shy to run your engine on the ground. This is one thing I do feel I did right and also feel it saved me from what could have possibly been a really bad flying day. There is a safe way to do this without harming your engine. I ran mine every week or two much to the jokes from others about "driving it around on the ground" rather than flying. I wanted confidence in my machine and look what I found! I'm not happy that I found debris, but thrilled that I found it while "driving on the ground"!! Its much better to correct the problem now rather than to experience it in the air. Much less adrenaline is involved.
I feel it is clean now and although I have confidence, I will be checking things again in a couple of hours to verify that the problem is completely resolved.
4) If you purchase a used engine with accessories as I did, take things apart with proper supervision and learn how it all works. Take the time to inspect it, clean it, and gather benchmarks on the overall quality and cleanliness of things. Like me, you only have others words to go by until you jump in and look closely for yourself. I trusted others too much and on some things I was plain ignorant.
5) If you're not hooking the engine up yourself, watch closely as it is being done. That is the one area that I did not watch closely. Its a fuel line! How hard would it have been to just undo it again and look in there for myself. Guys have handed me a rifle and told me that its unloaded. I still pull the chamber first thing and verify no bullets with my own eyes. Same applies here I think.
6) Just when you think you know it all, guess what?
