P0172 (bank 1 rich) & P0174 (bank 2 lean): injectors, O2 or HPFP?

MountainStone · 03-01-2018, 03:13 PM

This one has me stumped. These are the only two codes. Symptoms are occasional long crank and rough idle when cold, along with the SES light.

Most online searches recommend replacing the MAF, but the N54 doesn't have a MAF. The long crank makes me question the HPFP. I installed new plugs and air filter which made no difference, so I decided to seek professional help.

My local indy shop found and fixed a vacuum leak in the aluminum charge pipe (the meth bung plug was missing) and replaced the low pressure fuel pump. When the codes returned I called and they recommended replacing the O2 sensors. I decided to leave it with the local dealer. They recommended replacing the low pressure fuel pump. When I told them the pump was new, they recommended new injectors for $2800. I can replace the injectors myself so I told them "no thanks."

I hate to just throw (expensive) parts at this thing; does anyone have experience or reasoned troubleshooting advice?

MountainStone · 03-04-2018, 06:15 PM

Has nobody responded because this problem is too difficult or because it's so easy I should already know the answer?

dsjr2006 · 03-05-2018, 03:32 PM

Try posting in the forum for your engine. This is the general forum. I assume you have an N54 since you mentioned one in the post?

What are the codes you mentioned?

Boo$ted_in_ri · 03-05-2018, 09:43 PM

I had long cranks and rough cold idle. Shadow codes for fuel pressure. Changed my hpfp and problem was solved. Also had sputtering under heavy throttle.

03-01-2018, 03:13 PM	#1
MountainStone Private First Class 23 Rep 105 Posts Drives: 08 335i Sedan Join Date: Sep 2010 Location: Tejas iTrader: (0)	P0172 (bank 1 rich) & P0174 (bank 2 lean): injectors, O2 or HPFP? This one has me stumped. These are the only two codes. Symptoms are occasional long crank and rough idle when cold, along with the SES light. Most online searches recommend replacing the MAF, but the N54 doesn't have a MAF. The long crank makes me question the HPFP. I installed new plugs and air filter which made no difference, so I decided to seek professional help. My local indy shop found and fixed a vacuum leak in the aluminum charge pipe (the meth bung plug was missing) and replaced the low pressure fuel pump. When the codes returned I called and they recommended replacing the O2 sensors. I decided to leave it with the local dealer. They recommended replacing the low pressure fuel pump. When I told them the pump was new, they recommended new injectors for $2800. I can replace the injectors myself so I told them "no thanks." I hate to just throw (expensive) parts at this thing; does anyone have experience or reasoned troubleshooting advice? __________________
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03-04-2018, 06:15 PM	#2
MountainStone Private First Class 23 Rep 105 Posts Drives: 08 335i Sedan Join Date: Sep 2010 Location: Tejas iTrader: (0)	Has nobody responded because this problem is too difficult or because it's so easy I should already know the answer?
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03-05-2018, 03:32 PM	#3
dsjr2006 Captain 157 Rep 848 Posts Drives: '01 E39 540iA, '09 E90 M3 Join Date: May 2013 Location: Metro Detroit iTrader: (1) Garage List 2010 BMW 335i [0.00] 2001 BMW 540i [0.00]	Try posting in the forum for your engine. This is the general forum. I assume you have an N54 since you mentioned one in the post? What are the codes you mentioned? __________________ E90 M3 DCT LCI \| E90 LCI N54 M-Sport(retired) \| E90 Technical Docs download: http://j.mp/bmwe90docs *good read, very detailed.
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03-05-2018, 09:43 PM	#4
Boo$ted_in_ri Private First Class 30 Rep 159 Posts Drives: 2011 335i Join Date: Apr 2017 Location: RI iTrader: (0)	I had long cranks and rough cold idle. Shadow codes for fuel pressure. Changed my hpfp and problem was solved. Also had sputtering under heavy throttle.
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