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P2177 Lean off idle - 1 year later


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arankaspar1
New User

Oct 14, 2020, 5:07 PM

Post #1 of 5 (184 views)
  post locked   P2177 Lean off idle - 1 year later  

Hi all,
Need some troubleshooting next steps...
This ECU has a GIAC tune from 08', K04 turbo/forge diverter valve, bigger injectors.
I never had a CEL in the two years I've owned it for software. Tune has not changed but the engine has.
Motor lost oil pressure and died at 103k mi. (Common for these crap motors) Mechanic said the valves were bent and the air intake system flooded with oil.
I got it replaced with the same motor (BWT) from a dismantler and installed by a family owned well reviewed german mechanic shop repaired w no warranty because it's a pull. ($1.5k parts/ $4.5k labor)
Since getting the car back I've had this lean P2177... fuel trims shoot to 24/25 (max) on acceleration, only above 1500RPM. Short trim tends to stay within +2 and +9 (spec).
Clear the codes and the trims again skyrocket to max within 30 sec. of driving. Two days after clearing a CEL will come on with P2177 System too lean OFF Idle (acceleration).

Troubleshooting so far...

I'm lead to believe it's not a vacuum leak because trims only jump on acceleration but you all may know better.
However at idle if I hold accel. at 1500RPM in neutral the STFT dips -10 for 8 seconds then comes back up to +6ish then +1.

Mechanic who did the swap said replace the MAF sensor, Smoked intake twice and said there can't be a vacuum leak, has to be fuel related.
I kept an eye on my fuel pump duty cycle which we replaced because the duty cycle was around 85% at idle. Replaced fuel filter also.
Mechanic found low fuel pressure and checked the hard-lines and we replaced Fuel Pump Control Module... fuel pressure is in spec but P2177 still plagues us.
I replaced MAP, MAF and high pressure fuel line sensor, brand new OEM from ECS. Still no luck.
I have checked the PCV and rear main seal, swapped the coils with my old ones.
I'm now consistently getting a misfire on cyl 3 which was way more intermittent before on 2 & 3. Checking the spark plugs tomorrow.
Wide open throttle timing results below...



Only thing I can think of checking next is Fuel Injectors, O2 sensors, Knock sensors and maybe Low pressure fuel sensor... wondering if you have some old-faithful troubleshooting steps for these.
I don't believe the tune is the issue as all tuner companies I've called confirm that the software can't change or erase itself. The motor swapped in is the same (and used) so that I believe that to be the only variable.

I just registered it so it is behind on smog now. (As I understand the CEL is an automatic failure).
I very much appreciate your help and thanks for reading!


(This post was edited by arankaspar1 on Oct 15, 2020, 1:15 PM)


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Oct 14, 2020, 5:43 PM

Post #2 of 5 (179 views)
  post locked   Re: P2177 Lean off idle - 1 year later  

Sorry, we don't get involved in modified operating systems



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



arankaspar1
New User

Oct 15, 2020, 1:18 PM

Post #3 of 5 (146 views)
  post locked   Re: P2177 Lean off idle - 1 year later  

I completely understand. I'm just looking for some tips in how to troubleshoot these things. The modified computer was working fine for 10 years. If I hadn't mentioned it you likely help me with the same info I'm asking for help with. Just wondering how you all like to test injectors, O2 sensors and the like. This has nothing to do with the computer.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Oct 15, 2020, 1:51 PM

Post #4 of 5 (136 views)
  post locked   Re: P2177 Lean off idle - 1 year later  

Does this have a Catalytic Converter?

Have you done vacuum testing at idle and 2000 RPM to determine if there is any restriction?



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



arankaspar1
New User

Oct 26, 2020, 6:39 PM

Post #5 of 5 (70 views)
  post locked   Re: P2177 Lean off idle - 1 year later  

Yes, it has a stock cat. I tried to pull vacuum on it with a borrowed gun but I didn't have the right fitting. I'll go get a vacuum gun and test that. I need to cap off the host to the turbo and airbox right?
Also going to test fuel pressure on the schrader valve.


(This post was edited by arankaspar1 on Oct 26, 2020, 6:44 PM)






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