Gave some thought to fail safe mode and remembered that I have seen the fail safe mode happen when the MAF was bad, especially under hard acceleration. I have seen the fail safe come on and even go out after a restart. I common symtom is that if will not idle, stalls but will start back up. But the tech test is to disconnect MAF and see if the engine runs fine. If it does, don't bother trying to clean it, replace it.

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas