M3 Stalling Mystery: Fuel Regulator or Something Else?

As a 2010 BMW M5 owner, I faced nearly identical symptoms last year. The unusual stalls, power loss, and erratic idle were exactly what I experienced. After diagnosis, it turned out to be a failed High-Pressure Fuel Pump (HPFP). The repair was quite serious, as the faulty pump was causing improper fuel delivery to the engine. My car was in the shop for 3 days for the complete replacement. The mechanic also checked the fuel pressure regulator and fuel lines while they were at it, but the HPFP was definitely the culprit. These symptoms are pretty classic for HPFP failure in BMWs. You'll want to get it checked soon because running with a failing pump can potentially damage other components. My suggestion would be to head to a BMW specialist rather than a general mechanic for this specific issue. After the repair, the car ran like new again, no more stalls, steady idle, and full power restored.

Thanks for sharing your experience! that sounds exactly like what I'm dealing with. I've been worried it might be the HPFP, definitely doesn't sound like a cheap fix. Do you remember roughly how much you ended up paying for the whole repair? Also, has everything stayed running smoothly since then, or have you noticed any other issues pop up?

Hey there! Just wanted to follow up about my M5's repair costs. Yeah, the whole thing set me back about 1510 € for the HPFP replacement. Not exactly pocket change, but honestly, it was worth every penny. Initially I was worried like you about the fuel volume regulator too, but that got sorted during the repair. I'm really glad I bit the bullet and got it fixed because my car's been running like a dream since then, no more power drops, stalling, or any of that scary stuff. It's actually been about 14 months now since the repair, and she's still purring like a kitten. The BMW specialist I went to really knew their stuff. They explained that letting a faulty HPFP go too long could've caused way more expensive problems down the line. Trust me, I know it's a tough pill to swallow cost-wise, but getting it fixed properly is definitely the way to go. Better than playing the waiting game and potentially ending up with bigger issues.

I finally took your advice and got my car checked out. Turns out you were spot on, it was the HPFP. Found a good BMW specialist who really knew what they were doing. The whole ordeal took about four days, and yeah, it wasn't cheap at all, but the car's running amazingly now. The funny part was when I first drove in, the car stalled right in front of the mechanic's bay! Talk about perfect timing to show them the problem. They were super thorough, checked everything while they were at it, and even found a slightly worn fuel line they replaced just to be safe. The difference is like night and day now. No more unusual stalls, the idle's perfect, and the power delivery is smooth again. Should've done this weeks ago instead of worrying about it. Thanks again for pushing me in the right direction, you really saved me from what could've been a much bigger headache down the road!