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Gradaully worse stutter leading to P0171


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//UPDATE// Problem solved, see post #8.


Hello all,


Yesterday, I noticed my car backfiring every so often while idling at stop lights, which it has never done before. The idle back firing got progressively worse, until it started to do it while driving (mainly around shifts), then the CEL went on and the cruise light started flashing. My AP said it is a P0171, lean mixture in bank 1.


I've been reading many a thread on the P0171, and before I go mucking around trying to chase down the root cause, I wanted to post a log of me driving around town with a couple of 3rd gear pulls from 2000RPM to just under redline when getting on the interstate. I couldn't get all the way to redline due to running out of on-ramp.


I edited out the time between the two pulls, nothing much to see. Notice how the A/F learning A is wayyy out of tolerance, my peak boost is only 10psi, and my A/F ratio is around 17 when in closed loop. Fortunately, the DAM is still 1 and there's no knock under load, but it feels very anemic with the low boost.


If anyone skilled in the art can tell me if they have seen this before, or can point me in the right direction, I would be grateful. Thanks for your time!



- BNR 18g

- Torque Solutions TMIC

- 740cc DW

- Walbro 255lph pump

- SPT CAI w/ AEM filter

- Catless uppipe

- Catless 3" TBE

- Infamous tune, was running around 18 psi peak


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My stage 3 set-up w/an 18g was identified to be leaking (upon engine flex) where the (AVO) TB hose enters the TB. Fixed w/t-bolt clamp. Now boost is banging up against the limit....~23.3, despite loosening the WB actuator arm...
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Fix your leaks.
Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs.
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Finally was able to take a look at it today. The intercooler-to-throttle body hose was indeed loose, a common issue with this damn Torque Solutions piece of crap TMIC. It has been loose in the past, but never thrown a code.


Anywho, after making sure it was back where it should have been, I cleared the code and starting logging again. My AFRs are back to normal, and it doesn't backfire at idle, but after about 25 minutes of driving, I still have low boost and high AF Learning 1 A. Should I reflash with my latest rev from Infamous1?

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When I fixed the TB hose, I cleared the code and reset the ECU, went driving, logged, then posted what happened.


Since then, I have reflashed the ECU with Shamar's last rev (which has been on the car since last September with no issues). Attached is the log with a decent 3rd gear/2k to redline pull around t=1220. AFRs at idle are ok still, boost is only hitting 11psi, and the AF Learning 1 A isn't as high as before, but still >5%.


I will have new intake manifold gaskets tomorrow, so I will tackle that job and see what happens.


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Problem solved! :spin:


Got the new style manifold gaskets, they went in perfectly. Upon moving around the wiring harness bracket behind the manifold, I noticed one of the vacuum lines at the blue tee under the TMIC was almost off. I couldn't see it before, but that may have been the culprit. A couple of pulls later and everything looks and feels good to go.


If the gaskets weren't the problem, well at least I have new ones in.


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