[Gamzek]

So I hadn't changed the tune at all after it was dialed in at 12.0 AFR at full throttle. Yet yesterday as I was WOT in 2nd at 5k RPM it started creeping from 12.0 to 14.0+(I didn't keep going to see how high it wanted to go). I pulled out the laptop and changed the values from 4.5k rpm - 5.5k rpm at 10 psi - 11psi. They were previously at 9.7s, but now no matter what value I use(10.7 made no difference) it keeps creeping lean. Any ideas why it might be doing this is much appreciated. Thanks guys

 

[S/X Runner]

I do not have an awnser for you. But I would to hear the anwser. Gadget??

 

[Stroked01SRunner]

We're you starting to hit the fuel cuttoff?

 

[jakew88]

sounds like your fuel upgrades cant keep up with the rpm and boost. pushing a lot of air. but your fuel cant keep up. it might have been fine before but you fuel pump could be going out. a number of things. thats what it sounds like to me. you can tell the computer to put as much fuel as you want but it can only pump out as much as the equipment will let it.

i could be way off here but thats my guess

 

[Gamzek]

Currently I am using 318cc injectors with a walbro 190 fuel pump (from the URD fuel upgrade kit). The fuel system was sufficient until about a week ago. It seems that this only happens in second gear. Third gear now spikes rich on my AFR gauge at 5500 RPM 11psi due to my newly entered value of 10.7 in the R4 software (opposed to the 9.7 which created a 12.0 AFR for my truck a few days ago). I did install 2 new oxygen sensors to pass inspection around a week ago as well. Could the new oxygen sensors be effecting my AFR at all?

I am going around 65-70 mph at the top of second when this is all happening and my fuel cut-off is currently at 110 mph.

 

[XRobber]

injector failing?
Fuel pump failing?

 

[[email protected]]

The son of the guy that own's Unichip had the same problem recently. Their tuners could not figure it out and told him to call me. I told him to replace his fuel filter with a new Toyota/Denso fuel filter from the Toyota dealer, not some other brand. His problem was solved.

If that does not solve your problem, then I would put a fuel pressure gauge on the system and see if the fuel pressure is dropping. If it is there are two things left, fuel pump or fuel pressure regulator.

With the 2.2" pulley the URD injectors should be hitting just a hair over 80% duty cycle so you have plenty of head room left. But, if you can't get enough fuel at the right pressure to the injectors then it does not matter what injectors you have.

Gadget

 

[TahoesHateMe]

I've also seen Mass Air Flow sensors go bad at high RPM. I've watched the Grams per Second on a scan tool, it stops reading at a certain load and rpm then it starts to lean out.

 

[Gamzek]

Awesome, thank you much for the replies and the suggestions. Looks like I am getting a new fuel filter tommorow, thanks Gadget. TahoesHateMe, are you talking about OBDII diagnostics? I'll check that out as well, just haven't noticed that monitor on my program.