Codes P0171 and P0174

Hi,

I have to be honest. Both codes are related to a lean fuel mixture. I can't see how repairing an oil leak will fix it. If they are simply cleaning the engine to find leaks, I guess I could understand that. However, it really isn't needed. The problem you have is most likely related to either a vacuum leak or weak fuel pressure.

Do me a favor. Here is a link that explains how to find and repair an engine vacuum leak. Try it at home and see if you can locate the leak. It isn't hard. Just follow the link.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Next, if you are unable to find any leaks, the next thing I would check is fuel pressure. Although they replaced half of the system, there could still be an issue. Here is a link that shows in general how that is done.

You will need a fuel pressure gauge to do this, but most parts stores will lend or rent you one.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

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Here are directions specific to your vehicle for testing. The attached pics correlate with the directions.

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2010 BMW 328xi Sedan AWD (E90) L6-3.0L (N51)
Check Fuel Delivery Pressure (N51,N52 ,N52K) [REP-REP-RAE6313N52-1331029 - V.2]
Vehicle Powertrain Management Fuel Delivery and Air Induction Fuel Pump Fuel Pressure Testing and Inspection Component Tests and General Diagnostics Check Fuel Delivery Pressure (N51,N52 ,N52K) [REP-REP-RAE6313N52-1331029 - V.2]
CHECK FUEL DELIVERY PRESSURE (N51,N52 ,N52K) [REP-REP-RAE6313N52-1331029 - V.2]
Repair instruction
Check fuel delivery pressure (N51,N52 ,N52K )
13 31 029 | REP-REP-RAE6313N52-1331029 - V.2

13 31 029 Check fuel delivery pressure (N51,N52 ,N52K )
image
Special tools required:

13 5 220

13 5 221

13 5 222

11 4 310

Important!
Fuel in fuel lines is under pressure (approx. 5 bar).

Catch and dispose of escaping fuel.

Necessary preliminary tasks:
Switch off ignition.

Remove acoustic cover

Remove dust cap (1).

Pic 1

Procedure with the 25 bar pressure sensor:

Connect the set of special tools 13 5 220 (consisting of 13 5 221 and 13 5 222 ) to the pressure sensor of the BMW diagnosis system.

Connect pressure sensor to the BMW diagnosis system or IMIB.

pic 2

Important!
Do not screw in shutoff valve up to mechanical limit position under any circumstances.

This could damage the valve in pressure regulator housing.

pic 3

Install set of special tools 13 5 220 at injection pipe and tighten knurled nut hand-tight.

Unscrew shutoff valve (1) so that valve in pressure regulator housing is closed.

Establish fuel delivery pressure.

Screw in shutoff valve (1) until a pressure reading is displayed on BMW diagnosis system or IMIB. Read off fuel delivery pressure and compare with values in BMW diagnosis system.

pic 4

Procedure with the 100 bar IMIB pressure sensor:

For the check of fuel delivery pressure with the 100 bar IMIB pressure sensor only tool 13 5 221 is needed from the set of special tools. Unscrew special tool 13 5 222 from special tool 13 5 221.

pic 5

Install special tool 13 5 221 at fuel injection pipe and tighten knurled nut hand-tight.

Unscrew shutoff valve so that valve in pressure regulator housing is closed.

Screw onto special tool 13 5 221, the special tool 11 4 310.

Screw IMIB 100 bar pressure sensor on the special tool 11 4 310.

Establish fuel delivery pressure.

Screw in shutoff valve until a pressure reading is displayed on IMIB. Read off fuel delivery pressure and compare with values in BMW diagnosis system.

Note:
Removal of the set of special tools 13 5 220 :

-
Stop engine.

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Fully unscrew shutoff valve

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Remove set of special tools 13 5 220 from pressure regulator housing

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Catch and dispose of escaping fuel

Note:
Read out the fault memory of the DME control unit.

Check stored fault messages.

Delete fault memory.
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Let me know if this helps or if you have other questions.

take care,
Joe