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      09-11-2019, 11:25 AM   #1

Drives: BMW 135i
Join Date: Sep 2019
Location: Northern Europe

iTrader: (0)

N54 Fuel-related fault codes and symptoms


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!
Appreciate 0
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