2.5turd Posted January 31, 2018 Share Posted January 31, 2018 2005 Legacy GT, ej255, grim speed intake, aftermarket up-pipe and down-pipe. V3 accesport. I am having an issue with my rpms and fuel correction fluctuating when holding at certain RPMS. This happens throughout different maps. I tried cleaning the MAF but it remains the same. I will be trying to do a boost leak test tomorrow. Could this be caused by anything else? Faulty front o2? Throttle Body? I'm trying to get it tuned so I need to resolve this ASAP. ex: trying to hold rpm's at 2000 it will bounce between 1800-2000. It will rev up to 2000 then drop to 1800 and rev back up to 2000 and just continues. Same thing happens when trying to hold other rpms +/-200 rpms. At idle it does not do this. Here are some examples of A/F corrections while I'm fluctuating between the 1800-2000 mark. -20.31 -25 -25 -24.22 -17.97 -1.56 25 25 25 21.09 16.41 7.81 -2.34 -16.41 -22.66 -25 -25 -21.88 -8.59 13.28 25 25 25 19.53 13.28 4.69 -7.81 -20.31 -25 -25 -25 -19.53 -2.34 22.66 25 25 22.66 17.97 10.94 0 -13.28 -20.31 -25 -25 -22.66 -11.72 7.03 25 25 25 19.53 13.28 4.69 -7.81 -18.75 -24.22 -25 -24.22 -17.97 -1.56 24.22 25 Link to comment Share on other sites More sharing options...
relative4 Posted January 31, 2018 Share Posted January 31, 2018 Wow that's crazy, and it could be ANYTHING. Short list of things to test: Vacuum leaks Fuel pressure Upper & lower O2 sensors swapped Bad upper O2 sensor Bad MAF sensor Bad PCV valve No codes at all? Do you get stable LTFTs in any of the A-D ranges? Link to comment Share on other sites More sharing options...
awesterner Posted January 31, 2018 Share Posted January 31, 2018 Has your MAF been scaled for that Grimmspeed Intake, or are you just using the standard Cobb Stage 2? Link to comment Share on other sites More sharing options...
Spec-Ben Posted February 1, 2018 Share Posted February 1, 2018 Check your MAF connector (bend the cable while watching your AP, make sure pins are clean etc)... I had weird A/F Learning issues and and it took me forever to figure out that all I needed is a tierap... Link to comment Share on other sites More sharing options...
2.5turd Posted February 3, 2018 Author Share Posted February 3, 2018 Fixed my problem after addressing areas of potential issues. FYI. Steps: 1. Checked for vacuum leaks. No leaks. 2. Cleaned MAF. Reset the computer, ran another data log, and the problem still there. 3. Checked for boost leaks. (I will add a video of a cheap DIY boost leak tester when I'm finished editing it). My intercooler had a huge leak. And my PCV valve was malfunctioning, pressure was not building up it was just going right into the engine. Fixed the intercooler leak. Reset the computer, ran another data log, and the problem still there. 4. After thinking it may be the O2 sensor, I went and bought a new Denso blue wrapped front O2 sensor. On my way home computer through a code for the front O2 sensor, yay! Fixing the boost leak must have played into this as I drove literally 500 miles without a single code before. Replaced the O2 sensor and now things are hunky-dory. Fuel correction numbers are close to one another and RPM surge is gone. Back to the tuning process.... RE: PCV valve replacement. It's easier to get to by taking the intercooler off. Took some fiddling getting it out of the hoses with the stock crappy clamps on there. The PCV valve itself is in the plastic Tee housing really really tight. In fact I broke the housing to pieces trying to get it out no one had a PCV valve assembly including dealers less than a week out... I bought a new PCV valve, and disassembled the old assembly, put the new valve in and JB welded everything back together. Replaced the crappy clamps with normal people clamps. Tip, if its below 0 degrees F like where I live, warm the hoses up with a hair blow dryer first to make things slide in a little easier. Good Luck! Link to comment Share on other sites More sharing options...
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