Less Power and misfires on X5 50i M Sport - sorry for the long descriptions

[R2X]

Hello everybody, I'm new to this forum and have seen some great advice from the members. Hopefully you guys will have some good advice for me.

I noticed about two days ago that my 2013 X5 started driving more like my 6 cylinder Acura than the BMW power house I bought not too long ago. It was idling perfectly smooth and running normally but it was much lower on power - no sputtering etc. I have 66800 miles on the car and I've only owned it for about 6 weeks (Carfax didn't show any issues and only routine maintenance at the dealer) . The dealer told me it's time for spark plugs when I took it in for an oil change right after I bought it. They only offered that it's necessary every 6 oil changes and not that they'd seen a problem.

It was very powerful up until two days ago. I decided to push it to full throttle on the way home and I got it into limp mode. It's never done that to me before that day under the same load. When I got it home I was able to read codes P0305, P0306 and P0308 indicating misfires on cylinders 5, 6 and 8. This was with a basic scanner and not Carly. I shut off the engine and started it back up. The reduced power light was gone but the car still feels more like a smooth grandma mobile than the beast it once was. I cleared the codes later and I'm still in grandma mode, no sputtering etc. The only anomaly was that I heard what sounded like a belt squeal once or twice on starting the car and the day I got it into limp mode I had excessive squealing and a cloud of smoke from the front of the car when I started it to drive home, it only lasted a few seconds. I thought it was the belts but a little too coincidental to leave out of the diagnosis.

3 Questions -
1. Would the car suddenly go from perfect to 3 spark plugs misfiring overnight?

2. If I replace the spark plugs, is there anything I need to reset on the computer in the same fashion as brakes and oil changes require?

3. I'm thinking this might be an HPFP issue in it's early stages since all of those misfires are on the same bank of cylinders (correct me if I'm wrong there please)? I had talked to another BMW owner while shopping and he said the dealer replaced his HPFPs and the car car seemed to gain 100 horsepower. Prior to that he had no idea there was a problem and never had any check engine lights. Somehow the dealer found it without the owner pointing out an issue. Maybe it was just recall work.

I haven't found any threads that seem to relate to this exact scenario but any pointers and insight are appreciated. Thanks in advance for your help!

[R2X]

Here's another update. I tried WOT again today and got a new set of error codes. This time it's staying in limp mode even after shutting down and restarting twice. I've got an appointment at an independent mechanic next Monday. Here are the codes - insight or advice would be greatly appreciated.

P01C8 - Permanent
P142E - Pending

[TKR]

Those faults seem to relate to fuel pressure and high pressure fuel pump problems.

Bank 2 HPFP failure could explain those symptoms. I don't know if the HP pump could "squeal" when dying but in theory it's possible as they are mechanically driven...

[R2X]

Thanks TKR, I was thinking/hoping they were fuel pump related as well but didn't find a lot out here for those two codes. I'm going to try and bump up my appointment at the mechanic and I'll post back what we find out. It also turns out that the spark plugs were replaced about 17,000 miles ago so I won't be replacing them unless they are shown to be worn out in some way.

[Thecastle]

Ah, the squeal gives it away. Had the same problem, rough running, limp mode, check engine light (eventually)

You have a vacuum leak (squealing and misfire). My bet It’s your ribbed Ccv cross over house has become crispy. These fail all the time, it’s a 40 part easy diy. It sits under your engine cover and is the cross over pipe. Mine squealed smoked, etc. they turn to total crap and just looking at them they crumble. I think there is even an extended warranty on the Ccv system.

Your filtered air ducts, and entire pcv system are probably toast or very crispy as well.

This is hopefully your entire problem, smoking too would be expected with the Ccv cross over pipe. There of course can be more wrong.

[R2X]

UPDATE: The mechanic says that its the HPFP on the bank on the left. I should get the car back tomorrow and I'll post the results of whether it's entirely back to normal or not. Fingers crossed!

[R2X]

Seems it's back to normal after replacing the HPFP. No more codes at wide open throttle. It still seems a bit less sporty but not terrible. Do these cars tone down if you're not driving them hard constantly?

[X5 MAN]

Bad fuel from previous owner. Add fuel cleaners like Seafoam , 2 bottles at every fill-up for the next half a dozen fill-ups.

My 2011 X5 50i gained normal power after I started adding fuel stabilizers .It also cleans the injectors.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[R2X]

Thanks Gary!