Problems after removing a whipple setup

[agrump]

I decided to go back to stock and removed my whipple supercharger. When I flashed back to stock, I got an ECM error P0630. I read this has to do with changing the rear end which I had done, I went from 3.73 to a 3.15 while it had the Whipple tune. With the stock tune in place I used the flare tool to change the rear end to a 3.73 and back to the 3.15. This got rid of the error code but I have a problem with drivability.

When accelerating in second gear, the car is slow and I can see the vacuum building as it heads toward redline. There is also a huge power hole in third gear at 3000 rpm which also has a high vacuum at wot. It's like the throttle mapping is wrong. The car runs smooth, it just doesn't have any power.

Does anyone have any ideas what might be wrong?

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[agrump]

Ok, turned out that the factory tune can not cope with the 3.15 differential or the equivalent tire size change. Once I put the 3.73 back in, all was fine.

 

[Smunczen]

Glad you got it fixed.

 

[BrianH87]

Old thread, but I just went through this. This pointed me in the right direction. Thanks a bunch. I originally changed tire size through the tomahawk while the whipple was on. When I removed the whipple and flashed back to stock with FJDS, the factory tune wasn't happy. P0630 and U0422 were the result. I ended up having to run a comparator for my BCM as-builts vs my current ones. Found the discrepancy and corrected. No more CEL!

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