P0171/P0174 nightmare!!

[jr325i02]

So I have been troubleshooting my car for the past 3 months. I started with the maf sensor" the original was ok so it was not replaced " and replacing the vacuum lines, replacing intake boot " because it was cracking". I cleaned the intake valve very carefully as to not stress the gears. Replace the CCV valve. Replaced the fuel pressure regulator / filter, which improved pressure readings. Had the system vacuum tested with the smoke machine " no leaks" replaced evap valve the one that takes the fumes from the gas tank.
Replace camshaft position sensor and crankcase position sensor "both because of recurring codes with them"
Had the fuel pump checked "" in working condition""
Recently had both pre cat O2 oxygen sensors replaced as a last resort. To no success.
Checked my ignition coils and they were all in working order.
NOTE: I don't think it's going to be my fuel injectors,ignition coils, spark plugs because I find it very very hard to believe that two ignition coils or two fuel injectors would fail at the same time in different banks giving me Bank 1 and bank 2 lean readings. Also I'm not getting misfires in any of the cylinders
That was my original belief also with the O2 sensors but I change them and got THE SAME CODES!!!
P0171!!! P0174!!!P0171!!! P0174!!!P0171!!! P0174!!!P0171!!! P0174!!!P0171!!! P0174!!!P0171!!! P0174!!!
So what could it be????

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[etexis]

Obvious vacuum issue which engine


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[jr325i02]

But the system has been smoked tested twice and they didn't find any vacuum leaks??

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[All2kool]

Does the DISA hold vacuum?

[EdwardStewart]

Any mods like Cold Air Intake by chance? Also, there are some vacuum plugs on the back side of the intake that crack. When does the code show up, idle or while driving?


2005 330ci ZHP 6MT
2005 330i ZHP AT (Sold)
1989 325i
1990 318is
2014 328d X-drive
2017 VW Alltrack

[jr325i02]

Does the DISA hold vacuum?

Would I get a code for that? Oh the DISA had a vacuum leak which I fixed

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[jr325i02]

Any mods like Cold Air Intake by chance? Also, there are some vacuum plugs on the back side of the intake that crack. When does the code show up, idle or while driving?


2005 330ci ZHP 6MT
2005 330i ZHP AT (Sold)
1989 325i
1990 318is
2014 328d X-drive
2017 VW Alltrack

It's all stock besides a reusable k&n filter. The oil from the filter after I would clean it would give me bad readings on my maf but that was quickly solved by cleaning the oil residue off the maf sensor with MAF sensor cleaner

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[EdwardStewart]

The shop that did the smoke test, did they not run a scan to look at the air/fuel ratio? They should be able to tell if it is running outside of the appropriate range. As you have done new oxygen sensors, the problem is generally a vacuum leak causing the problem.

Have a scan done at idle, that is generally where your car will exhibit issues if it is a air/fuel ratio problem. Someone had asked about the DISA, the valve can be checked off of the car by manually closing it and then placing your thumb over the vent. If it is good, the valve will hold open.

The gasket on the DISA can also leak, causing a vacuum leak, but I would look at the air/fuel ratios first with a scanner before exploring anything else.


2005 330ci ZHP 6MT
2005 330i ZHP AT (Sold)
1989 325i
1990 318is
2014 328d X-drive
2017 VW Alltrack

[etexis]

Well if you need to get it scanned out here in SoCal I can do so for 80 I’m in Orange County


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[EdwardStewart]

Here is a good article to read.

http://wiki.ross-tech.com/wiki/index.php/Fuel_Trim_Info


2005 330ci ZHP 6MT
2005 330i ZHP AT (Sold)
1989 325i
1990 318is
2014 328d X-drive
2017 VW Alltrack

[whiskychaser]

In the same boat. Car starts first time every time and has no misfires. It might help isolate your problem if you have the fuel trims read. If the short term fuel trims are high at idle but drop when you rev the engine, that suggests you may still be looking for a vacuum leak. (At idle, the amount of unmetered air may be comparatively large because the throttle is shut but it does not have as much bearing on the mixture when it is open). Also, the fuel pump may be working but are you getting the right pressure and flow now? Pretty sure the specs for yours are the same as mine - 51 psi and 1.1 litres every 30 seconds.

[All2kool]

Oh the DISA had a vacuum leak which I fixed.

Please elaborate on this.

Also, what is the result when you check the DISA to be certain it holds vacuum?

[EdwardStewart]

The DISA valve essentially has a flap that opens and closes based on throttle input to lengthen the intake runner. To test the DISA, remove it and push it closed from the position it is removed and then place your thumb over the vent that is located on the diaphragm assembly. It will be apparent when you remove it.

The gasket that you will see on the DISA Valve Assembly is known to leak on occasion and can cause a vacuum leak as well.
http://www.germanautosolutions.com/b...repair_kit.php

The link should explain everything and these kits are well done if you need to rebuild the DISA.



2005 330ci ZHP 6MT
2005 330i ZHP AT (Sold)
1989 325i
1990 318is
2014 328d X-drive
2017 VW Alltrack