2.7 to 2.5 engine swap

[vandal123]

Here goes, So I purchased a 1988 e30 325i engine. I have the computer for it no wiring harness.I own a 1985 e30 325e. I put it in anyways. I used the original 1985 wiring harness and computer and fuel injectors and cold start injector. The engine I used the whole engine changed the fly wheel and the harmonic balance for timing. I used the intake manifold and throttle body from the 2.5 . I turned it on it runs rough like a vacuum leak and probable pre detonation.

any ideas why it runs rough?

do i need the wiring harness?

do I need the oil cooler?


anything helps thanks

[MR 325]

The swap is not even worth doing without running the 325i wiring harness, computer, AFM, ICV, TPS, injectors, flywheel, etc.

[Varinn]

Get the harness, you've got a complete mishmash of fuel injection parts. The b25 and b27 are very different motors and need very different tuning. I'm about to do the same swap but I made very sure to pillage every single underhood component related to the engine and the electrical.