Cold weather rough start

Well,  I am using Mogas 91 AKI.. and the other Bob, I believe is using 100LL.

Today we had 42F OAT and a pre-heated engine to 80F oil temp.   I was getting 290 RPM while cranking with the fuel pumps off (verifying my problem is not a junky battery or starter).    I set the throttle to 65% as recommended here.. and cranked the engine.   It ran rough for approx 1/2 second and smoothed out.  I quickly reduced the RPMs from approx 2800 down to the recommended 2000rpm.

Perhaps the issue was that setting it to 50% was just too low.  I'll update this again as more test data becomes available.

So..  now that it's a bit warmer out these days..  I found that today I had the same issue..  it took about 4 or 5 attempts to get the engine started.  Of course, I only filmed the last attempt (duh) when it did start , but the Oil Temp was 85F (29C), OAT was 73F (23C) today..  battery voltage was (after 4 attempts) still good at 13.0v.  On all attempts, throttle was set to 65% as indicated by the EFIS..

I'm not really sure what could be the matter with it.. other than some sensor not working properly.  Thinking about putting a BUDS dongle on it to record data soon.  The plane started flying April 2021 and this past winter was the first time I started to have this trouble..

The only real thing different about this past winter was that I'm using the REIFF preheater..  and the heat was turned on last night.. though things warmed up nicely thoughout the day.. i could have done without it today.