A/F Correction

[HolyCrapItsFast]

@HolyCrapItsFast I managed to remove the O2 sensor and the car becomes very lean between 3k and 3.5k and it idles on 15.8AFR log below:

https://drive.google.com/open?id=0B6zn_kRV08vAU2JxYi1EX2NvOWs&authuser=0

I think that is the wrong log. :tup: I am not seeing any of what you are seeing. If you did, in fact, unplug the O2 sensor then the column "CL/OL Fueling" should be "10" all the time and A/F Correction #1 will show no activity.

Can you do it again and make sure that it was in fact the O2 sensor you disconnected? Also please reset the ECU before the test.

Much appreciated!
George

 

[welaish]

[MENTION=9]HolyCrapItsFast[/MENTION] Oh sorry you are correct here is the correct file. https://docs.google.com/file/d/0B6zn_kRV08vAYkhzc3g4aEU3Wk0/edit?usp=docslist_api

 

[welaish]

The Cl/Ol fueling 7 actually not 10 and ecu was reset. O2 sensor was disconnected because check engine light was on when I disconnected with the correct code.

 

[HolyCrapItsFast]

Yes 7... I knew it wasn't 8. This tells me it is not the sensor but something with MAF calibration or a leak. The fact that you suggest it was fine and then suddenly bad suggests a leak. :tup:

 

[welaish]

[MENTION=9]HolyCrapItsFast[/MENTION] but why its at the maximum when 3k rpm?

 

[HolyCrapItsFast]

I have no answer... All of your other logs suggest an issue trough out the driving range because learned shows corrections throughout, not just at 3000. It just happens to occur more at 3000 so it seems and perhaps that is the right condition to make it more prevalent.

 

[Spamby]

[MENTION=9]HolyCrapItsFast[/MENTION] but why its at the maximum when 3k rpm?

I had seen where Cobb and other tuners suggested a 10% variance was acceptable on the gr/gv chassis due to the FPR setup. Given how these cars are funky at the 3k mark and above 5k, with fuel trims, it doesn't surprise me that the issue becomes more prevalent around the 3k mark.

Also, vacuum leaks, post turbo, become boost leaks under pressure. This may have something to do with your load and the way the ecu is seeing it. I could see a minor leak calling for 10% more fuel, but once your vacuum becomes less and you rise to boost, this leak may seal to a degree under less vacuum prior to being blown open in boost.
I am of the understanding that small leaks may become less prevalent once more metered air is added to the system, or should I say the leak is masked by the larger amounts of metered air.

I've been following this thread out of curiosity because I'm, once again, experiencing a high LtFT at cruise and at the magical 2700-3000 rpm spot. Once I add some throttle, the fuel trims even out to normal and she's fine. I also have zero drive ability issues or idle issues. I'll be tearing her apart over the long holiday break and working from the filter to the block in order to find this "mysterious" leak.

 

[welaish]

[MENTION=9]HolyCrapItsFast[/MENTION] thanks for your efforts. [MENTION=1507]Spamby[/MENTION] makes sense will look for a leak again. Its very difficult to find it. Let me know what happened with yours.

 

[Spamby]

[MENTION=9]HolyCrapItsFast[/MENTION] thanks for your efforts. [MENTION=1507]Spamby[/MENTION] makes sense will look for a leak again. Its very difficult to find it. Let me know what happened with yours.

I've ordered new gaskets for the IC connections and a new IC to TB coupling. All zip ties are going away replaced by clamps... on vacuum lines. Any worm clamps will be replaced by t-bolt clamps. Pressurized parts will have t-bolt clamps with tension springs. I plan to also pressure test the IC itself as well as the intake tract. Fuel pressure will be tested, as well.
Fun times.

 

[HolyCrapItsFast]

FUEL PRESSURE REGULATOR!

I'm almost certain. You should check fuel pressure at an idle with the vacuum hose disconnected and clamped off.

 

[qht_sti]

I've ordered new gaskets for the IC connections and a new IC to TB coupling. All zip ties are going away replaced by clamps... on vacuum lines. Any worm clamps will be replaced by t-bolt clamps. Pressurized parts will have t-bolt clamps with tension springs. I plan to also pressure test the IC itself as well as the intake tract. Fuel pressure will be tested, as well.
Fun times.

Hi. I've been chasing the same issue on on my car ( 2011 WRX STI) that just started out of the blue for the last 5 weeks. Were you able to find a solution ?

 

[welaish]

[MENTION=4963]qht_sti[/MENTION] installing FPR this week. It should be sorted after the installation. It came suddenly also without any mods.

 

[welaish]

[MENTION=1507]Spamby[/MENTION] what is your update on the issue?

 

[qht_sti]

@qht_sti installing FPR this week. It should be sorted after the installation. It came suddenly also without any mods.

Thanks. I'll also replace it and see if it sorts it out.

In my case the issue came up about two weeks after being tuned with a walbro fp , DW 850 injectors and meth injection. I initially suspected the new injectors and changing back to the stock injectors and map didn't fix the issue.

 

[welaish]

I guess your problem is different. You might need full fuel rails. Because you are using bigger injectors.

 

[Spamby]

[MENTION=1507]Spamby[/MENTION] what is your update on the issue?

Found a leak at the intercooler y-pipe connection. Replaced those gaskets. Found the turbo inlet had slipped a bit off of the turbo. Replaced with a t-bolt clamp. Replaced BOV gasket and throttle body gasket. Replaced IC to throttle body coupler. Replaced IC coupler clamps with t-bolt clamps. Traced all lines and connections. No other leaks found.
I've gained a stronger manifold vacuum by about 2 in hg settling at 21 in hg during idle. Boost comes on super quick and the car runs like a scalded dog but.... fuel trims are still at 18% positive on the LtFT. I have no issues driving now other than a wicked stumble or stutter right at peak torque, 4k-4.5k rpm.
I still need to test fuel pressure. I'm leaning towards this being in the fueling.

 

[HolyCrapItsFast]

Found a leak at the intercooler y-pipe connection. Replaced those gaskets. Found the turbo inlet had slipped a bit off of the turbo. Replaced with a t-bolt clamp. Replaced BOV gasket and throttle body gasket. Replaced IC to throttle body coupler. Replaced IC coupler clamps with t-bolt clamps. Traced all lines and connections. No other leaks found.
I've gained a stronger manifold vacuum by about 2 in hg settling at 21 in hg during idle. Boost comes on super quick and the car runs like a scalded dog but.... fuel trims are still at 18% positive on the LtFT. I have no issues driving now other than a wicked stumble or stutter right at peak torque, 4k-4.5k rpm.
I still need to test fuel pressure. I'm leaning towards this being in the fueling.

When are you going to let me see a log?

 

[welaish]

Exaclty! Any leak in the intake will make the fuel trim skewed even after you fix it. I had also more vacuum 22 after fixing my leak. But fuel trims is still the same. +16. I dont have even the stumble. I see only AF correction reaches +25 between 3000 - 3200 rpm. It lools like vacuum is traped somewhere in the fuel lines(stupid guess).

 

[HolyCrapItsFast]

[MENTION=1507]Spamby[/MENTION]... Did you reset the ECU?

 

[Spamby]

When are you going to let me see a log?

Probably need to get that to you. Lol