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09-11-2019, 11:25 AM | #1 |
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N54 Fuel-related fault codes and symptoms
Hello,
For over 2 years I've owned a MY 2008 135i, N54B30A now with 217k kilometers (or about 135k miles) on the dash and I've experienced different kinds of fuel-related symptoms in the past months: -Cranks a bit longer than usual when cold starting, engine near stalling every time, then appears a message in iDrive for "Engine fault, restricted power". This limp mode can also be activated when trying to pass another vehicle/wide-open throttle. When you stop and start the engine again, this disappears and might not go into limp mode again, especially when the engine is warm. -Occasionally I get limited revs in about 3500-4000rpm (maybe due to low fuel pressure, no limp mode when this happens) -Occasional rough idle and twitching, which is noticeable when using cruise control. -Fault codes: *29F1 / Fuel pressure plausibility *29F2 / High-pressure fuel system, fuel pressure *29F3 / Fuel pressure sensor, electric The 29F2 code is present for most of the time, others are not. Fault codes can be deleted, but will reappear after a while. I have catless downpipes, an upgraded FMIC and a performance catback exhaust fitted in the car. It has been tuned before, but at the dealer's shop they updated all the software, including the fuel system. So no tunes anymore... I think it's best not to tune it again before this problem is solved. I've always filled up the tank with 98-octane gasoline and the car is in good condition otherwise. Do you have any ideas where to start with? Obviously I have tried to delete the fault codes and reset adaptation values for the fuel system without success. I'm aware of the HPFP failures in N54s, but I would not like to start from there, just in case it could be something else causing the problem. Sorry for the long post, but I tried my best to make it readable with all the info I have so far. Thanks in advance! |
09-25-2019, 09:36 AM | #3 | |
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Quote:
In addition to my previous, yesterday I experienced even more rough idle and poor acceleration. Got the following fault code in wide-open throttle at 4000rpm: *29DC / Cylinder injection cut The fault code 29F2 was also present, as it is every time when the car enters limp mode. Is this another fault code pointing towards HPFP as the cause of these problems? I had the fault memory read also with ISTA+ software. For the code 29F2 present at the moment, it suggested changing the flow-control valve. Where is this located? I couldn't find any information from the web about this... |
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04-26-2021, 06:20 AM | #4 |
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The problem in this situation indeed was the HPFP, after replacing one faulty injector. I decided to replace the pump with a fresh OEM one, with the new part number. Haven't had problems ever since. The previously mentioned flow-control valve is a built-in part of the pump.
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