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Old 10-28-2013, 12:50 AM   #9 (permalink)
t vago
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Originally Posted by UltArc View Post
What about if it is in Drive, like the OP is doing it?
The answer depends on three things - selected transmission gear, the stall rating of the torque converter, and the vehicle speed. If all three are such that the transmission can still turn the engine over, even if it's turned off, then the engine turning will then drive the transmission oil pump. As long as the transmission oil pump continues to be driven, then it is still circulating fluid throughout the transmission.

I see this happen fairly regularly with the Karen-mobile, in fact. Whenever it enters DFCO (normally in D at speeds above 50 MPH and with no pressure on the gas pedal), the engine computer will cut power to the injectors, and the engine will still turn over, due to the fact that the drive wheels are now driving the engine through the transmission. Below about 50 MPH, though, the engine computer will "start" the engine again by re-energizing and driving the injectors as before. I suspect that if this did not happen, the engine would probably come to a stop at some point not far below 50 MPH, as transmission oil pressure would drop to a point where it could not hold its selected gear any longer, thus disconnecting the drive wheels from the engine.
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