I have a 2011 STi sedan that has had issues with what seems to be stumbling at about the 3500 rpm range at about 25% throttle. I've been noticing this problem for a little while but it has become more prevalent in the past few weeks. I know the stock fuel pressure sensor had issues with this at some range, but I upgraded to the Cobb FPS a couple years back when did the "Stage 2" mods and switched to run on E85. I had my tune at JM and haven't notice any other issues. Any thoughts on issues or questions for more detials would be appreciated.
Do you have the ability to datalog fuel pressure? I've seen folks comment that the COBB "stumble fix" didn't actually fix the stumble and/or even made the problem more prevalent. In those cases, it sounded like an aftermarket FPR was the only solution.
I have an accessport, I'll look into if I can log via that. I'll take a look at that. I guess I should mention that I upgraded the to the Cobb FPR not an FPS. Should I look into another?
Did you get the full cobb e85 kit? One of them has a fuel pressure sensor that can tell you the psi of the return line and if the fpr is working correctly. If you are using this sensor, jm likely used a feature in cobb to adjust fuel injector duty cycle based on how far off the fuel pressure is in relation to boost.
I don't have the full kit unfortunately. I have been eyeing it as the flexfuel system would be nice to have as it seems E85 is becoming more scarce around here. Just have a few other more important purchases before I can get to that.
my 2009 wrx has this stumble at about 2500 RPM. This is a known issue, and from what I've researched is hard to tune around. It has always been there, through each different tune, etc. It hasn't made any difference to anything, Like you've stated, it is only noticeable under mild load, in a very specific RPM range. Just use more right foot...
