The reason I suspect the fuel is because you say it only starts to miss 1-2 minutes after startup. The glow plugs aid ignition for 1-2 minutes, once they shut off the compression ignition is all that will function. If the fuel is of poor quality it might just be good enough to run with the GPs heated but not good enough to fire well under compression ignition alone 100% of the time...just a theory but it would explain why it runs OK during that first 1-2 minutes.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz