[F90m5]

I purchased a relatively low mileage (54k KMs) F90 with what seemed to be no issues whatsoever after getting it "professionally" inspected pre purchase. Only issue i faced a couple weeks after purchase was slight RPM jittering DURING fueling. But that was the only thing and it didnt really bother me much as the car felt perfectly normal when driving, pulling, idling, etc...

About 2-3 months later on a random monday morning, about 5 minutes into a drive, the car has lost all power when accelerating. I stopped on the side of the road and saw that there was a major fuel leak coming from under the engine bay. I sent it to my mechanic and he came back to me saying one of the bolts that is holding down the High-pressure fuel pump onto the head cover in bank 1 snapped and needed replacement. So we went ahead and replaced it, and everything seemed to go downhill from there...

Ever since then, I have faced several issues and they are as follows:

- When the car is at idle, stopped at a traffic light for 2-3 mins, or just parked but switched on, I would get extremly rough idling and would eventually misfire cyl. 1 + 5-8.

- When pulling (even slightly) the car would almost instantly go into limp mode.

- During one pull I attempted, the exact same issue of the HPFP bolt snapping in bank1, happened on the second bank and HPFP.

-Exhaust is shaky. Seems to be in a pulsing manner quite aggressively.


Now, what I have done to try and solve this:

-replaced all sparkplugs TWICE.
-replaced all injectors, and coils.
-replaced both high pressure fuel pumps.
- replaced Low pressure fuel pump.
- replaced both fuel rails.
- done smoke tests for any Vac leaks. All good.
- No exhaust leaks either.

I am not a mechanic by any means, but I do know a thing or two. This has been going on for about 2.5 months, and im about almost at a dead end. Not to sure where to look anymore or what to do, and it seems as though my mechanic is on the same boat as me. Ive racked up a hefty bill with my mechanic, and really feel as though I'm missing something minor and Im only throwing money into parts unnecessarily.

Any help, previous similar issues, or suggestions would be really appreciated.

[carseatsm5]

Is the car tuned?

[F90m5]

Nope, Completely stock. No mods no tunes.

[Mr. Jonathan]

I have no clue what could snap HPFP bolts... never heard of it happening. Timing chain or solenoid issue maybe? Are you getting a CEL?

[Servonen]

Did you check errors by the OBD? Nothing?
Misfire on cylinders 5-8 means 5,6,7,8? It's like whole one bank... The same what got this issue with the HP fuel pump? I would check (swap?) injectors - they could collect some metal fragments and now doesn't work properly?
yes - I know you have replaced them, but did you have the same issues on the same bank before?

[hookson]

What codes are you getting?
Where are you located?

[crypto]

I’m not going to be of any help here but what do you mean RPM jittering during fueling? Like you don’t turn off your car when you add gas?!

[pbonsalb]

I was curious about that also — creating an evap leak does not help. But the OP appears to have more serious additional problems. I would have guessed LPFP but it has been replaced. I’ll guess the car had some prior work done that was not done right. Maybe a coolant tank failure requiring new injectors and during replacement a fuel rail bolt was cross threaded, stripping the threads in the hole, leading to injector vibration, damaging of the injector holes, and breaking the bolt. Just a guess — this is way beyond me. https://www.xbimmers.com/forums/show....php?t=1485638

[AHall]

You may have purchased a vehicle with pre-existing issues not detected during your pre-purchase inspection. I wonder if BMW would have a history of work performed or a diagnosis performed on the vehicle? If you have access to that information that may give you a clue. Who knows what the previous owner did to the car. Did you purchase the car from a BMW dealership? What year is the car?

[S EyeLand]

You check your air intake/ MAF sensor? Fuel filter? I had similar issues on a car where the charge pipe came loose. Did you have to change the coolant tank?

[Jambo1]

This is a classic case of throwing parts at a car hoping it gets fixed.

Did your mechanic walk you through what fault codes he saw?

A broken bolt on HPFP also just seems so random and suspect.

A good diag is key here, using a scan tool that can read live stream data.

[nordmanmg]

That can be a faulty fuel pressure relief valve, check fuel pressure on the ramp during engine idle and under higher RPMs. sounds weird that both HPFPs snapped bolts off themselves.