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Paxton Surging and Bucking...Tune Issues?

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dsp4848

dsp4848

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Have you flashed your car back to the stock file and tried flashing the Lund file again?
That has fixed some strange fuel trim issues before.

Your STFT and LTFT are fighting each other at idle. But that leaves your actual AFR right where it should be. Just an indication of possible other issues like EVAP stuck.

I think what you are feeling at part throttle is the VCT intake and exhaust being at 0. The intake cam at 0 is actually in the middle as it is a midlock phaser. Its kinda looks like you are meeting the load requirement for OP, but not the pedal so it is not phasing the cams to where they should be. Everything... spark, speed density, torque values, etc. all depend on the cams moving to the right position to get the right mapped point values. Being at 0 when they should be flowing through a few mapped points is not going to give you smooth results.

Instead of messing around in Excel, download SCT livelink Gen II. It will chart all the values for you and you can add histograms to compare two or thee values against each other.

I start with getting a new battery. Put it in. hook a battery charger up. flash the stock file. Then flash the lune file and see how it goes.
Sorry for the long delay in response. Been trying to move into a house and keep up with work travel as well.

Anyway, I did try this a couple of weeks ago - flashing to the stock tune and then to the Lund tune. I did notice that my LTFTs were reset to 0 across all RPMs. Upon startup, no issues whatsoever. Probably the smoothest startup and idle I've had since I was stock. I let the car idle for about 5 minutes and then took it out for a spin. It seemed much smoother on power delivery and after upshifts. I couldn't get the car to exhibit any bucking or surging. That is until the car started learning fuel trim values and mapping the LTFTs. After driving a bit the LTFTs started going deeply negative again (-10% to -25% depending on load/rpm, etc.). At least I have consistency here and the car was able to recreate the same situation from a fresh tune flash with cleared fuel trims.

I have opened up another case with Lund and will attempt to get this sorted out with them. Thanks for the feedback and I will post another update once I know more.
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BFord1

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I have a procharger d1sc with a gt350 intake and the same issue. Mine is also tuned by Lund. I did data logs and paid them for a retune as. Bought the car already modified. They looked at the data logs and said that my fuel trims were all over the place and that it wasn't my tune. They suggested checking for a exhaust or vacuum leak. I haven't found either. It's frustrating. I've had one person tell me it could be the gt350 intake. Had another tell me it's the Kooks headers because of where the O2 sensors are mounted and suggested changing to American Racing headers. But I'm not going to just start buying new parts and hope for the best. Im curious to see if you get it resolved. Good luck.
 

robmustang201528

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I'm in the same boat as you guys except my wrench light comes on and leaves me on the side of the road smh. It starts to surge then I can slowly feel it losing throttle, then a wrench light comes on with a airbag light smh. I'm taking it to ford Monday. My rack and pinion also when it out. I turn it to the right its stiff as hell. Most of the time when I turn the wheel hard to the right it would throw a wrench light but now it's doing while the car is driving straight. Im hoping the rack and pinion is the reason why the wrench light keeps coming on since it's all electrical but now...while driving stright on the highway it just started to surge and throw a wrench light. Can't find any vacuum leaks or boost leaks either.
 
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dsp4848

dsp4848

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I have a procharger d1sc with a gt350 intake and the same issue. Mine is also tuned by Lund. I did data logs and paid them for a retune as. Bought the car already modified. They looked at the data logs and said that my fuel trims were all over the place and that it wasn't my tune. They suggested checking for a exhaust or vacuum leak. I haven't found either. It's frustrating. I've had one person tell me it could be the gt350 intake. Had another tell me it's the Kooks headers because of where the O2 sensors are mounted and suggested changing to American Racing headers. But I'm not going to just start buying new parts and hope for the best. Im curious to see if you get it resolved. Good luck.
Got another tune from Lund that has been a lot better. When they turned off adaptive fuel control, I couldn't get the car to buck/jerk on accel and my startups are very smooth. It appears that when Lund has adaptive fuel control active in the tune, the STFTs and LTFTs are both active. When they disable adaptive fuel control, the LTFTs are turned off (always 0). With this new tune with the LTFTs off, I don't have my STFTs and LTFTs fighting each other, which is what I think was causing the issues I was having. I'm still working with them to determine now why my STFTs are often negative (vary from about -10% to 25%), but at least I'm making progress. Just as a note, I've noticed that my STFTs are negative on light throttle and/or when going downhill. When there's some load on the engine, i.e. going uphill or accelerating, the STFTs usually look good (-10% to +10% worst case). WOT is still about -10% to -15% on the STFTs though.

Another thing that I noticed when adaptive fuel control is turned off is that the IM Monitors CAT, O2, and H02 will never complete. This might be a solution, or at least something to look in to, for others who have had trouble getting their tuned car to pass inspection.

I'm in the same boat as you guys except my wrench light comes on and leaves me on the side of the road smh. It starts to surge then I can slowly feel it losing throttle, then a wrench light comes on with a airbag light smh. I'm taking it to ford Monday. My rack and pinion also when it out. I turn it to the right its stiff as hell. Most of the time when I turn the wheel hard to the right it would throw a wrench light but now it's doing while the car is driving straight. Im hoping the rack and pinion is the reason why the wrench light keeps coming on since it's all electrical but now...while driving stright on the highway it just started to surge and throw a wrench light. Can't find any vacuum leaks or boost leaks either.
Was it surging when you were just cruising or were you accelerating? Sorry to hear you're having other issues as well, that's got to be super frustrating. Let us know what Ford says.
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