Fluctuating AFR under WOT (jpg and log file included)

[suprasick]

For the past two weeks I have been noticing under wide open throttle my air/fuel ratio goes scary lean. The only code that shows is 34, which from my understanding, is from fuel cut. I am running the stock ct26 hooked up to stock wastegate not shimmed (roughly 12PSI). That alone seems weird to me... maybe my intercooler is really efficient?

MODS:

Cxracing Intercooler 2.5" pipes with a recirculated freddy BOV
Innovate LC-1 wideband
3 Inch no cat exhaust
Stock ECU with knock sensor rewire with sheilded cabling
Stock Fuel System
Stock AFM with aftermarket cone filter
New Denso o2 sensor as of last year

What I've done:

Re-set timing
Calibrated TPS

Here is a sceenshot:

Here is the log file from logworks


Any input would be great as I am stumped where to start with this problem.

Thanks in advance!

 

[MK3Powah!]

what is your timing set at?

 

[suprasick]

10 Degrees BTDC with te1 and e1 jumpered

 

[IndigoMKII]

You don't have a pre-turbo vacuum leak do you?

 

[suprasick]

I swear I checked but it will never hurt to check again. I'll check again today.

Is there any other information or something I can do to make it easier to diagnose through the internet?

 

[IndigoMKII]

Check your fuel pressure, you could have a pump that isn't switching from 9v to 12v. The switch can be checked by jumping fp and b+ in the diag box and taking it for a quick drive.

 

[suprasick]

For reference I thought I would post my findings....

After finding a fuel pressure tester that would fit the CSI banjo bolt, I noticed the fuel pressure was always at 40PSI. After further investigation it turns out I had hooked the fuel pressure vsv backwards so that it would not allow vacuum to flow through at idle. I am still not 100% on how the system works, but all it well according to the TSRM.

From my understanding vacuum is applied to regulator bringing fuel pressure down to 32PSI.
When under a boost scenario vacuum is taken away from the regulator (obviously) and fuel pressure rises.
The VSV portion of the system is only to aid in hot starts by taking vacuum away from the regulator raising fuel pressure.


So all in all i'm not sure how in my particular case of hooking the the vacuum hoses backwards would cause my problem (it would just leave the regulator HIGH all the time) but putting it the right way solved my problem! Now I have a steady AFR 11.5-12 under WOT

Now it's time to make sure my EGR VSV is all in order....:cry:

 

[jetjock]

Ironic since Toyota designed that setup to be fail safe. You're right, you don't understand how it works. Both the FPR and three way solenoid valves. Lucky you didn't toast your engine...

 

[CyFi6]

So all in all i'm not sure how in my particular case of hooking the the vacuum hoses backwards would cause my problem (it would just leave the regulator HIGH all the time) but putting it the right way solved my problem! Now I have a steady AFR 11.5-12 under WOT

The regulator also increases fuel pressure with boost.

 

[jetjock]

The regulator keeps the delta P constant. It's as simple as that.

 

[suprasick]

Ironic since Toyota designed that setup to be fail safe. You're right, you don't understand how it works. Both the FPR and three way solenoid valves. Lucky you didn't toast your engine...

I know! It looks like I have more reading to do.

The regulator also increases fuel pressure with boost.

So the regulator is not just on (vac) or off (atmosphere) it also restricts fuel as boost pressure rises to keep fuel pressure constant?

The regulator keeps the delta P constant. It's as simple as that.

I've noticed in almost every post you write in any thread I always end up reading a lot! Looks like I have some physics to catch up on.

Thanks for your reply

 

[CyFi6]

Yep like JJ said its job is to maintain the same pressure difference between the fuel rail and the intake manifold regardless of engine load, so pressure in the rail rises and falls according to manifold pressure.

 

[jake8790]

Something still isn't right, your AFR's should be in the 10's at full throttle on the stock ECU.

 

[suprasick]

After resetting the TCCS, my AFR range under WOT is 10.5-10.8.

Thanks again to those who helped.

 

[jetjock]

Something is wrong. There's no way "resetting" could cause that.