Power Loss Around 4000 RPM

New to tuning, working on the VE table for my 2005 Jeep Wrangler 2.4 turbo. It is set up to make 5 psi boost maximum, so I am tuning it closed loop based off the LTFT until my wideband arrives.

So far the thing runs fine, working out the VE table still, but the computer keeps it stoich in closed loop. I figure 5 psi at stoich won't cause any issues with 93 octane and retarded timing. I can drive it around, shift through all the gears, and get up to speed, but if I try to get it up to 4000ish RPM, it sort of sputters and hits a wall, won't go any faster. It feels sort of like the limp mode kicking in. I had a code p2074 for MAP/TPS correlation being off that I disabled because obviously the ECU does not expect 15 psia at part throttle and I figured that was throwing the code. I wonder if disabling the code forced a limp mode above 3900 RPM or something. Another possibility is too little spark advance, but you can look at my base tables and data log and it doesn't really drop off and knock sensors don't kick on at all. Does anyone have any ideas? Most recent tune and data log are attached, feel free to peruse. Attachment 99770Attachment 99771

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Originally Posted by tschmitt416

New to tuning, working on the VE table for my 2005 Jeep Wrangler 2.4 turbo. It is set up to make 5 psi boost maximum, so I am tuning it closed loop based off the LTFT until my wideband arrives.

So far the thing runs fine, working out the VE table still, but the computer keeps it stoich in closed loop. I figure 5 psi at stoich won't cause any issues with 93 octane and retarded timing. I can drive it around, shift through all the gears, and get up to speed, but if I try to get it up to 4000ish RPM, it sort of sputters and hits a wall, won't go any faster. It feels sort of like the limp mode kicking in. I had a code p2074 for MAP/TPS correlation being off that I disabled because obviously the ECU does not expect 15 psia at part throttle and I figured that was throwing the code. I wonder if disabling the code forced a limp mode above 3900 RPM or something. Another possibility is too little spark advance, but you can look at my base tables and data log and it doesn't really drop off and knock sensors don't kick on at all. Does anyone have any ideas? Most recent tune and data log are attached, feel free to peruse. Attachment 99770Attachment 99771

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I know that on the NSRT-4 platform, this "limp mode" associated with the P2074 code continues to kick in even when you disable the P2074 code in the DTC portion of the tune. So, you'll get the limp mode without the CEL/stored code. It would always pop up on 2005 model year Neons, as they had more stringent diagnostics protocols than the earlier years. It's related to the expected airflow given a certain TPS vs Engine Speed. With that being said, it's possible you may be able to increase the airflow model limits found in the [Engine Diag] [General] [Torque Correlation] section of the tune, if you have the tables labeled Airflow Max RPM and Airflow Max TPS.

I don't know if this will fix the P2074 limp mode and/or prevent the code from popping up. A good test would be to re-enable the code in the DTCs, max out the airflow limits of those tables, and see if the code ever pops back up or not. It should become immediately apparent if the wall at 4k RPM is alleviated by doing this, also.

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Originally Posted by B00STJUNKY

I know that on the NSRT-4 platform, this "limp mode" associated with the P2074 code continues to kick in even when you disable the P2074 code in the DTC portion of the tune. So, you'll get the limp mode without the CEL/stored code. It would always pop up on 2005 model year Neons, as they had more stringent diagnostics protocols than the earlier years. It's related to the expected airflow given a certain TPS vs Engine Speed. With that being said, it's possible you may be able to increase the airflow model limits found in the [Engine Diag] [General] [Torque Correlation] section of the tune, if you have the tables labeled Airflow Max RPM and Airflow Max TPS.

I don't know if this will fix the P2074 limp mode and/or prevent the code from popping up. A good test would be to re-enable the code in the DTCs, max out the airflow limits of those tables, and see if the code ever pops back up or not. It should become immediately apparent if the wall at 4k RPM is alleviated by doing this, also.

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Hmmm yeah the Jeep computer is very similar, but I don't have those options under engine diag. I just found a TSB for this code that might actually eliminate this issue. I know other people with turbo 2005 2.4L Jeeps that do not have this issue. I wonder if the dealer would be kind enough to flash my computer for free lol. I can't think of any way around this other than maybe trying to flash a Neon tune to my Jeep... if they're the same computer could this work? Seems like a possibility to brick the PCM though. It's silly to pay a dealership to flash my ECU when I have this software though.

I am having a very similar issue. Did you ever figure it out?