Engine running for a few seconds after key off, hard gear changes

So a few weeks ago did a complete A/T transmission flush including dropping the pan and changing the filter. As well i pushed through about 10 quarts of T-IV ATF through it by using the oil cooler line as a drain with the engine running.

The butt dyno says that the truck feels more powerful, not because anything with the engine changed, but for the increased efficiency of power being delivered through the transmission. Two things that have cause for concern/interest came up.

First, often when i turn the truck off, the engine will still turn for a second or two, as if its being fuel starved to shutdown. I assume the increased efficiency of the new fluid is maintaining the centrifugal momentum inside the torque converter after the fuel is shut off, turning the engine from the transmission. Am i correct in my assumptions? Any concern for this?

Second, when shifting from first to second, the A/T tends to slam into gear. Ive been automatically letting off the gas when i can sense its about to change in oder to alleviate this. Any insights?

 

usually dieseling of an engine (still running with power turned off) is because there is too much unburned fuel being supplied which could also be a result of not enough air to lean it out.

I cant see how any of that can be connected to a tranny flush but did you reset the EFI? changing the tranny power output will distort the fuel air ratio so it needs readjusting, reset it if you haven't already done that and see if that sorts things out

 

I had a switch on the EFI relay to shut off the engine (fuel supply) while i was pumping the fluid out (I didnt have a helper to turn the key off for me).

I did get some cool P16xx OBD codes out of it. Also i blew the 7.5 amp ECU fuse.

I went ahead and pulled the battery cable for the hell of it, it is still doing the same thing. Its slowly becoming something im just dealing with. I would like to figure this out before it just becomes second nature to driving my truck.

@CodeSeven

 

well im thinking its gonna be a leaking injector until you can absolutely 100% rule that out by checking the cylinders with a bore scope to be sure none are leaking after shut down.

in order to diesel after shut down it has to still be getting "some" gas

 

Fuel thing on shutdown. See what would happen if you went to high octane. Could be the leftover fuel self igniting from excessive cylinder wall heat, and the knock sensors are compensating enough to not be noticable while driving. May have an intake leak. Or injector leak as previousely mentioned

Transmission thing. Thats expected. Your pressure solenoids inside the tranny now have thin and clean atf pushing them. Either you were heavy on the gas from the atf being dirtier, and this is the effect with the same heavy foot and cleaner atf, or the 2nd gear solenoid port is a little dirty and causing a higher pressure or faster liquid delivery, causing a quicker shift.

 

If you think it the torque converter turning the engine...then shut the truck off while in N. That will prove it has nothing to do with the tranny.