So today was the last day of my reassembly of the M50 under the hood of my 525. I did a runup test and I'm getting an odd problem.

It starts fine. Idles fine and clicks. Just click click click right on the top of the engine. If I hold it at 3k it stays there for about 5 seconds surges to +500 rpm, then the engine shuts off. I can then immediately start it again and it has the same sound and issue.

The computer has no error codes.

Anybody have any ideas what it could be?