M20B23 engine swap to M20B25

[antonni95]

I have a 5 speed 85 323i and a spare M20B25 from a 88 325iS - apart from simply removing the old and dropping in the new, what else is needed? I know it is going from L-jetronic to motronic so the ecu will be replaced but what else has to be changed? Wiring loom - full or just engine? etc

thanks

[ross2009]

just the engine loom need changing it goes thro a grommet near the battery tray its pretty easy swap

[antonni95]

cool, thanks

[Kedge]

Not going to be that easy actually.

Since you're going from a M20B23 you'll have the old style small square C101 plug, whereas all 325i's have the later round C101 plug. This is where the engine loom connects to the cars main loom by the fuse box.

Best bet i think will be to source the C101 from a 325i car with a few inches of wiring and splice it in, or you change the whole car loom instead..........i know people have gone down the route of changing the whole car loom doing this swap.

Here's the wiring info for the two different plugs;
http://www.e30zone.net/e30zonewiki/index.php/C101

You'll want all the M20B25 ancillaries, loom and ECU as well since the '88 M20B25 will be running Motronic 1.3