E38 / T43 auto in drive downshifting throttle blip problem on 06 Corvette
The patient is an 06 Vette with heavily modified E38 LS3 440ci 600HP and stock 6180e T43 with a stock 08 tune in it (does the same thing with stock 06 tune). The problem is that when the car is coming to a stop and it starts downshifting automatically as the car slows, each time it downshifts something is bliping the throttle just a little bit. I can see it while monitoring, the throttle position when I let off the gas goes to 23% but as it downshifts the throttle goes up to 24 or 25% momentarily which in turn raises the RPM by 200 to 300 RPM. This is just enough to cause the car to lurch forward with each down shift. In town driving is crazy with the car lurching forward every time I try and come to a stop. I put the stock transmission tune back in it to confirm its not that and it still does the same thing so it must be the engine tune. It does it three times which I believe is the 5 to 4 shift, the 4 to 3 shift and the 3 to 2 shift. The faster I stop the worse the problem.
The engine has a large cam, big ported heads, fast 102 manifold and headers or and 3.15 gears in the rear. We have modified the tune extensively to make good power and drive ability, along the way we must have changed something. Max Idle area 1 B1651 to 2.9999 from 2.397 and Max Idle area 2 B1652 to 2.4994 from 2.3697 in an effort to get it to idle with the big cam (which it now does). Desired idle speed is now 725 in gear B1821. Many of the other idle tables have been modified to get it to run smoothly I don't think it is necessary to list all the changes here. Torque Management is turned on with all stock settings in place.
Does anyone know what table controls this downshifting throttle blip, I can't find it. Is it supposed to blimp on downshift in drive? I have played with all the idle tables and everything I can find that might be related but can't figure it out. Help!
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