[mittortz]

Hi all, new to this forum but hoping to pick some minds more advanced than mine. I have an 2004 M3 with 177k on the clock, lots of maintenance and big 3 done in the last 10-15k under my ownership. Car is in great mechanical condition and I've pulled it to redline many times without issue. However, about 3 weeks ago I had an issue with a sputtering engine when I came to a stop, which eventually progressed to a dying engine and then I was completely unable to get car running/keep an idle. This was preceded by a few months of the occasional rough idle and a couple instances of hesitation in 1st gear. I got suggestions to replace the fuel pump, and since it had never been replaced before, I bought a Hella-branded pump from Bimmerworld and put it in. Car fired right up and ran great for exactly 1 week (there were maybe 1-2 instances of slightly rough idle but very short lived; otherwise perfect). Now, whenever I start the car, I get an idle that chugs between between 500-1500 RPM; video here. Sometimes it settles, sometimes it dies. I can get the car going and drive pretty normally, but whenever I come to a stop, there's a 50% chance it won't hold the idle and just die.

Following this, I wondered if my Hella pump was a bad unit, but needed to confirm by doing some other things. So I replaced the fuel filter and fuel pressure regulator, and I also cleaned the ITBs, ICV, and MAF sensor. Started the car and the symptoms remained. So, I hooked up a pressure gauge to the FPR housing to get some readings. Pressure with pump primed is about 69 PSI, 4.75 bar (pic attached). Here's a video of a startup: pressure seems to waver between 4.5-5 bar, and strangely (?) eventually settles at 4.5 bar. I did a few different attempts and got mixed results, but this was fairly representative of what I'm seeing.

I don't have a SES light or any significant codes that I can tell​, but I'll post them below just in case. Unfortunately, my knowledge around auto-mechanical workings is pretty limited, but I'm trying to learn. I've gotten suggestions for cam sensors and vacuum leaks (going to learn how to do a good smoke test soon), but I'm not sure how to proceed otherwise. If anyone has any thoughts or advice, I'd be really grateful. I want my baby back and I'm trying to avoid taking it to a shop since I'm not exactly flush with cash right now.

Here are my codes (most of which have been sitting there for several months. The D7 is new, since the fuel pump replacement):
"D7 KOMBI tank lever-type sensor 2"
"A - Error line active seat left (no response from control unit) / Plate light right / Sunblind motor, open circuit"
"3D - GM: Boot-lid unlocking: mechanism"
"5E1A - DSC ECU: ECU internally: serial peripheral interface (SPI): translation error multi IC / CAN DME / DDE signal failure / CAN ENGINE 1 MOTBK speed signal invalid / Coil outlet valve (dump) shorted rear left"
"4F - Exhaust gas temperature sensor"
"F - Power-on reset"

If there are any other details I can provide, would be more than glad to. TIA

Edit: also maybe worth mentioning I've got a squeaky pulley/serp belt, which I intend to replace soon. Don't think that's related though from what I've read.

[M3ZCPNYC]

Crank shaft position sensors?

[M3ZCPNYC]

Sometimes the fuel pumps the wiring is tricky RK tunes out on Long Island really knows the fuel pumps on these cars and the wiring, maybe give them a call.