Hi, I hope to be swapping my existing engine with a rebuilt one in the near future.  The MR2 service manual and other sites all talk about unplugging the engine loom from lots of places and removing the loom with the engine.  As I will then be unplugging this loom from this engine and transferring it to the new engine I wondered about simply unplugging the loom from the engine, sensors etc, before removal.  Has anyone tried this alternative? Thanks

I meant to add, leave the loom in the car, and then reconnect to the new engine when it  has been installed.

There are changes in the 3sgtes, eg  sensors. So can you identify the year / version ? Is the new one from MR2 or Celica ?      

Both are 3SGTE gen II, mine a JDM from 1990 and the rebuild engine is from a 1993 JDM MR2.

1993 is a Gen 3 and old motor is a Gen 1 or 2. Total difference in plugs and Ecu managerment.

I'd love for it to have been gen III but definitely both gen II, gen II fuel rail, gen II intake manifold with TVIS, gen II injectors, gen II shim over bucket valve adjustment....  The only difference I've come across is that Toyota seem to have moved to the 9-stud exhaust manifold from the 7-stud.  The 9-stud is normally a gen III feature but it seems they brought it in towards the end of the gen II run.

Back to my question, if both gen II, would it make more sense to disconnect the engine end from the loom if I'm swapping engines.  Has anyone tried this rather than the usual technique of unplugging the loom from the various other ends, ECU, resistor packs etc, and taking the loom out with the engine.

I've take engines in and out maybe 20 times. Definitely take the engine out with the loom attached to the engine. Way too hard to be trying to remove and then reattach everything with the engine in the engine bay - not sure its even feasible tbh given space and access. No advantage I can see to doing it that way.