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Discussion Starter · #1 ·
Right at about half throttle 2300 rpms my CP3 swapped lml has a very rough and jumpy acceleration right before the torque converter locks. My data logs are showing that my fuel railpressure is constantly going above and below the commanded rail pressure at the exact time I felt the fluctuation. At times its barely noticeable and at other times it makes the truck feel like its in the middle of a paint shaker. This was happening before and after the custom tunes for the cp3 only now it seems to do it with a bit less throttle. WOT is fine and doesn't seem like the pump could be the issue. Any insight is appreciated.
 

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Discussion Starter · #4 ·
My first step would be to get in touch with your tuner, Duramax Tuner?
I have contacted the tuner already sent them the data logs and they're reviewing them but the guy on the phone didn't seem to really know what he was talking about. I decided to go with SDT but I hope I don't end up regretting it.
 

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If im reading those logs right, this is happening when desired and actual pressures are near 30K? Almost seems like the fuel pressure relief valve is popping open and close
 

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Discussion Starter · #7 ·
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If im reading those logs right, this is happening when desired and actual pressures are near 30K? Almost seems like the fuel pressure relief valve is popping open and close
That honestly sounds like it could be the issue but that doesn't explain why my WOT pulls smoothly. It happens right when the ECU demands 25k psi a little over half throttle. I took a couple more screenshots showing the WOT run with the engine load percentage.
 

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It maybe appears that your fuel rail pressure sensor is whacking out. Just guessing here, no live experience with graphs and explanations. Maybe some tuners here can chime in.
 

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Well, at WOT, you are using the pressure and not allowing spikes that would occur with half throttle, but perhaps it is the CP3 tuning during those times
 

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Discussion Starter · #10 ·
Well, at WOT, you are using the pressure and not allowing spikes that would occur with half throttle, but perhaps it is the CP3 tuning during those times
Damn tuning company sure is taking its time with tuning and probably gave me the wrong calibrations. I told them the truck had a fleece LBZ cp3k but maybe it's more to it than just a specific pump.
 
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