2008 550i Acting up

[kal476]

Alrighty... So.
A week ago I was driving my car a bit hard, enjoying the 72 degrees that came our way. I suddenly got a Engine Malfunction on the iDrive system. I had no power, and a very rough idle. I replaced the belt and two pulleys as they were squeaking. No problems.
A week later same thing happens, but the car stalls. I started it back up (Reluctant, took significantly more cranks to start) and had a super rough idle. I turned the car off, waited an hour, and all was okay. The malfunction cleared itself, and the car was fine for another two weeks.
Today I had the same problem, but no faults on the iDrive and no check engine light. I did however manage to pull these codes:
P0420 Cat Efficiency Below Threshold
C0300 Rear Speed Sensor Malfunction
P0600 Serial Communications Link Malfunction
P0004 Fuel Volume Regulator Circuit High
P2004 Intake Manifold Runner Control Stuck Open Bank 1

So far i've had a couple ideas of what the problem could be:
Fuel Pump
Spark Plugs/Coils/Injectors
ECM shorting out

That's all I can think of.
Basically along with the rough idle, I was able to push the accelerator down to the floor with an extremely delayed response. Car stalled, left it for an hour, started it up and all was fine. This problem only seems to occur when I drive the car harder than usual.
Anyone have this problem or any ideas?

Thanks!
-Kal

[CMYACHTIE]

Originally Posted by kal476

Alrighty... So.
A week ago I was driving my car a bit hard, enjoying the 72 degrees that came our way. I suddenly got a Engine Malfunction on the iDrive system. I had no power, and a very rough idle. I replaced the belt and two pulleys as they were squeaking. No problems.
A week later same thing happens, but the car stalls. I started it back up (Reluctant, took significantly more cranks to start) and had a super rough idle. I turned the car off, waited an hour, and all was okay. The malfunction cleared itself, and the car was fine for another two weeks.
Today I had the same problem, but no faults on the iDrive and no check engine light. I did however manage to pull these codes:
P0420 Cat Efficiency Below Threshold
C0300 Rear Speed Sensor Malfunction
P0600 Serial Communications Link Malfunction
P0004 Fuel Volume Regulator Circuit High
P2004 Intake Manifold Runner Control Stuck Open Bank 1

So far i've had a couple ideas of what the problem could be:
Fuel Pump
Spark Plugs/Coils/Injectors
ECM shorting out

That's all I can think of.
Basically along with the rough idle, I was able to push the accelerator down to the floor with an extremely delayed response. Car stalled, left it for an hour, started it up and all was fine. This problem only seems to occur when I drive the car harder than usual.
Anyone have this problem or any ideas?

Thanks!
-Kal

First fault is related to your catalytic converter, you don't say what your mileage is but I would suggest to have the cat checked first.