1997 528 sputters on start up

[miliue]

In a different direction, my car was doing something similar to yours and it turned out to be a failing MAF. Rough idle when starting up in the morning/after work. Lots of hesitation/low power/threatening to stall until the engine warmed up. I replaced the MAF yesterday and it now drives like a champ. It's an expensive sensor but if you've ruled everything else out, you might consider it. Or at least consider taking the MAF out and cleaning it with some MAF cleaner from your local auto store. I have a different motor than you (M60b30) but I would imagine MAF symptoms are the same across motors.

[genphreak]

@milue:

Just beware, different MAFs or perhaps just changing them can change the feed signal that the ECU has learned to live with. I recently changed one on my M50 (when it is probably my o2 sensor causing all the running at normal operating temperature troubles) and it ran great.

Then after a tank of fuel or so the troubles returned.

There are many sensors, in my experience one really needs to replace the O2 sensor and engine temp sensor every 100,000km and check things like MAFs if they are known. Else you have to remove and test them when you get running problems...