Symptom of fuel pressure problem.

I've seen this when the FPR fails which you've said replaced in a time frame that would not have failed but that is the most likely candidate.

Checking fuel pressure after engine off for example overnight it should still be 20-30#.

When wife's FPR failed, the psi would jiggle not stay steady.

The next most likely candidate is fuel pump. When they fail, it's a slow process that's masked by the FPR doing it's job.

On the v8s with "convenience start" that I've worked on, the fuel pump doesn't kick on at key on like the 3.0 models only once you turn to the start position so it's relying on some reserve pressure from the last drive.

If you have a scanner that can force the pump on you can prime the fuel rail before you crank to help diagnose.

You can use a cheap "throw away" tire pressure gauge for simple read of pressure overnight (in my testing this works for one session/day, it kills the guts and stops working) but for $1 dollar store gauge it works.

"Feels" like you'll be able to trace the problem within a few tests.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)