I've noticed the last 3-4 times I've started the engine (IO-520 BA), that there is a fuel (starvation?) issue maybe 5 to 10 seconds after the engine starts and stable at 1000-1100 RPM.
The first two times it caught me off guard and the engine shut down. After restarting, I kept the RPM a little higher and the engine behaved normally with no issues.
The last two times I was expecting it, so when the engine started to stumble, I turned on the electric fuel pump just long enough to keep the engine running smoothly and then I had no issues.
All run ups are normal after that.
The start up procedure has always been the same:
Throttle FULL, Mixture Rich, Battery ON, Fuel pump ON until the fuel flow stabilized (16-18GPH in 3-5 sec), Throttle back to idle and then add two turns, Ignition.
The engine starts after maybe one prop rotation and stabilizes at 1100 RPM.
The only difference lately is that the engine heater has not been on, but I don't think that that might be a factor.
Any suggestions/ideas of how to troubleshoot are welcome.