RomRaider

I have a 2006 Forester XT with a full 2007 STi driveline swap.
The car started life as an automatic. After the swap I had a very annoying rpm hang between shifts.
No amount of tuning we did could eliminate the rpm hang. MickeyD has been helping me greatly with this.

On a whim, I reached out to a member over on Nasioc who had quite a bit of experience with wiring merges and swaps and we started going through some things. On a totally random side track, I cut the wire to the speed sensor from the ECU and the throttle hang was completely eliminated. The car was transformed and was actually fun to drive again.

Problem is, now I have an annoying backfire problem. It is not horrible, but when I lift throttle between shifts, the car will pop, and when lifting throttle and decellerating (like going downhill coasting), the car will backfire a couple of times.

Now, when I hook the vehicle speed sensor back up, the problem goes away completely, but the rpm hang is back.

I know the speed sensor input to the ECU is tied to per gear determination thresholds, but it seems to me that it must also be referenced in other portions of the logic which may not be defined yet?

Keep in mind the Forester was an automatic before the 6MT swap, so it had a TCU (trans control unit) in the loop as well.

As it sits right now, the TCU is removed, it has a 2006 WRX ecu (+ ign. sw., immobilizer and key).
I swapped to the WRX ecu thinking that the Forester ecu was to blame for the RPM hang.
The throttle hang exists with either ecu installed.

Anyone have any experience with this?

The only other thing I can think of is to actually gut the interior and swap out the entire bulkhead harness from a manual tranny Forester to eliminate the auto tranny interfaces (TCU etc).

On the DBW cars, there is a idle mode switch right at 2kph. Above 2kph the car will idle higher. Below 2kph it tries to steady in on a very low idle.

Is the harness that plugs into the ECU the stock forester harness? I know on the 16bit ECUs you need to ground a certain pin to tell the ECU that the car is manual so even if you put a manual ECU in the car it would still function as if the car had an AT. Not sure on the 32bit ECUs as I don't have a service manual for those years.

^Let me know if you want any of the manuals... I have a few of them.