[Cinderwolf]

Recently, I was fortunate enough to receive a 2009 BMW 535XI as a gift. The car has had significant work done, including a transmission replacement, and while it has 188,000 miles and shows its age, it drives fine for now. The main issue I'm facing is limp mode, which I assume is related to the "Engine Malfunction, Reduced Power" warning. I'd like some advice on the best way to approach this.

Although I'm not experienced with car repairs, I want to at least buy the right parts and understand how to address this problem. Taking it to a mechanic every time isn't financially feasible, and many common issues with the car are well-documented. From what I've read, limp mode could be caused by things like cracked or broken boost lines, dirty or faulty solenoids, bad vacuum seals, or damaged charge pipes.

I'd prefer to tackle several potential issues at once, so I’m looking for guidance on the best approach. To be clear, I’m not looking to modify the car extensively, just to handle basic maintenance and fix common problems myself. Since I don’t have a driveway, I'd likely be working on the street, but luckily, I live in a part of Brooklyn with decent street parking.

My questions are:

• What parts should I buy ahead of time to address these issues, and should I buy them new or used as there many part outs in my area?
• Are there any upgrades I can make to simplify future maintenance and reduce its frequency?
• What type of charge pipe would you recommend?
• Should I replace the solenoids or try cleaning them with brake cleaner?
• Is there a roll of silicone hose I can buy to replace commonly failing parts?
• Is there a good way to best isolate what could be causing this problem?
• What tools would be essential for tackling these jobs?

The only other modification I plan is installing an Android screen from AliExpress, which should arrive soon. Hopefully I’m not in over my head, and I’ve found a few local people who do street maintenance that I could hire at a reasonable cost. But I really want to be hands-on and approach this with a clear plan.

The check engine light comes on and off, and I’ll try to get the codes soon, but any advice, videos, links, or suggestions would be greatly appreciated. I know the general idea is that this car is most likely a waste of time, but I guess a fell for the sunk cost fallacy as alot of money has been put into it and I do really like how it drives/feels. I'm not sure if buying a new car is feasible right now since I'm in graduate school and need to be smart with my money. Thanks for the read, also crazy ask but if you can explain certain parts and what they might do with clarity that would be immensily helpful (although this is not an expectation), and I hope this is a start to me becoming more mechanically literate.

[sparkyte]

Hello,

its definitely a start for you to become more mechanically literate when you got an 188 000 mile n54. For the limp mode, you will need to read the codes at least as it can be anything, at least get a direction. First you can tell us what has been done to the car as maintenance/mods as you said its quite some stuff. Also get to know what's the issue for the limp mode as it may be something serious and not a simple or cheap problem to fix, then start from there. There are a lot of videos on youtube, at least thats my main source of repair info for my car. Initial maintenance includes:

-spark plugs, ignition coils eventually checking the index of the injectors and if they are leaking or not
-water pump + thermostat
-belt + pulleys and while in there put a crank seal guard
-change to a metal charge pipe
-oil change
-does it have downpipes or cats? Does it have any smoke?
-eventually clean the solenoids too
-are there any leaks? Like valve cover, oil pan, oil filter housing?

[swellengear]

As mentioned above, limp mode can be caused by MANY things.

The first thing you need to invest in is a good code reader, or, better yet, a cable and a copy of INPA. This will be vital for N54 ownership.

[Cinderwolf]

For some update, I installed a 14.9' in android auto screen which has been great. I also got a new side skirt and front bumper, side skirt needs to be installed better as now I cant open the passenger side front door. I was finally able to run a diagnostic scan and here is what came up.

OBD-IIOBD-II
DTCs: 10
----------------------------
P2096 [0x2096]
Post catalytic converter fuel trim (FT), bank 1 - too lean
Post Catalyst Fuel Trim System Too Lean
Status: Confirmed
----------------------------
P2196 [0x2196]
Heated oxygen sensor (HO2S) 1, bank 1 - signal stuck rich
O2 Sensor Signal Stuck Rich
Status: Confirmed
----------------------------
P114B [0x114B]
Post Catalyst Fuel Trim Via Oxygen Sensor System Too Lean Bank 1
Status: Confirmed
----------------------------
2F7B [0x2F7B]
Status: Test conditions are met, Validated and stored in non volatile memory, Validated fault present at time of request
----------------------------
2C31 [0x2C31]
Status: Pending fault present during this driving cycle, Validated and stored in non volatile memory, Validated fault has been present during this drive cycle
----------------------------
2C2B [0x2C2B]
Status: Pending fault present, Validated fault has been present during this drive cycle
----------------------------
30FF [0x30FF]
Status: Test is inhibited by other DTC, Validated and stored in non volatile memory
----------------------------
2F9E [0x2F9E]
Status: Pending fault present during this driving cycle
----------------------------
2C7E [0x2C7E]
Status: Pending fault present during this driving cycle, Validated fault has been present during this drive cycle
----------------------------
CDA9 [0xCDA9]
Status: Test conditions are met
============================
Engine control unit
No DTC found.
============================
Transmission control unit
No DTC found.

At this point I'm trying to figure out what would be the best way to isolate what is causing the 30FF code, if anyone has any good ideas that would be amazing. From what I understand it can be anything from a turbo leak to a bad turbo. I'd at least like to diagnose it myself before I decide whether to take it to a mechanic or work on it myself. I have car scanner on my android autoplay so I can monitor the car as I drive it. It might be important to note that this issue has been going on for years and hasn't been isolated and fixed. The car starts right up and the amount of power I get varies sometimes, but the engine malfunction reduced power only comes up when I try to accelerate too fast. Thanks for your time and excited for any insight.

[Cinderwolf]

Also, here are some codes read by a different OBD reader when I had first gotten the car

[konstat]

Originally Posted by Cinderwolf

For some update, I installed a 14.9' in android auto screen which has been great. I also got a new side skirt and front bumper, side skirt needs to be installed better as now I cant open the passenger side front door. I was finally able to run a diagnostic scan and here is what came up.

OBD-IIOBD-II
DTCs: 10
——————————————
P2096 [0x2096]
Post catalytic converter fuel trim (FT), bank 1 - too lean
Post Catalyst Fuel Trim System Too Lean
Status: Confirmed
——————————————
P2196 [0x2196]
Heated oxygen sensor (HO2S) 1, bank 1 - signal stuck rich
O2 Sensor Signal Stuck Rich
Status: Confirmed
——————————————
P114B [0x114B]
Post Catalyst Fuel Trim Via Oxygen Sensor System Too Lean Bank 1
Status: Confirmed
——————————————
2F7B [0x2F7B]
Status: Test conditions are met, Validated and stored in non volatile memory, Validated fault present at time of request
——————————————
2C31 [0x2C31]
Status: Pending fault present during this driving cycle, Validated and stored in non volatile memory, Validated fault has been present during this drive cycle
——————————————
2C2B [0x2C2B]
Status: Pending fault present, Validated fault has been present during this drive cycle
——————————————
30FF [0x30FF]
Status: Test is inhibited by other DTC, Validated and stored in non volatile memory
——————————————
2F9E [0x2F9E]
Status: Pending fault present during this driving cycle
——————————————
2C7E [0x2C7E]
Status: Pending fault present during this driving cycle, Validated fault has been present during this drive cycle
——————————————
CDA9 [0xCDA9]
Status: Test conditions are [...]

30FF represents a boost leak. Quickest way to check for a leak would be to perform a smoke test. One you replace the leaking part the other codes could likely go away