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Discussion Starter · #1 ·
Hey guys, my e46 325xi has a lot of miles on it and I have a donor car that is a 320i. I would like to engine swap. Now as far as I know everything should line up. But how hard would it be when it comes to the ECU?
 

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Hey guys, my e46 325xi has a lot of miles on it and I have a donor car that is a 320i. I would like to engine swap. Now as far as I know everything should line up. But how hard would it be when it comes to the ECU?
Unless your current engine is damaged, I would keep it. The M54 engines in these cars will most likely outlast the rest of the car. I daily drive an '03 530i with 411k miles on it. Original engine and it has never been pulled from the car.

I suggest you make sure your maintenance is up to date on the M54B25 and keep driving it.

I haven't even mentioned that the M54B22 has 20 less hp and you have a heavier all wheel drive vehicle.
 

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the people’s mod
2004 330Ci 115k miles
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What are the production dates for both the 325xi and the 320i?
It always helps to provide details.

Both cars have the same MS43 DME (ECU). The 320i engine will start and run on the 325xi DME.
Then after all swap-related issues are resolved the 325xi DME can be programmed with 320i software.
 

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Discussion Starter · #5 ·
What issues are you having with the engine?
I’ve been having trouble with idle and loss of power at times. I replaced the thermostat because the engine would never heat up. Which fixed the issue for a short while but then one day it wouldn’t heat up and eventually had oil blasting out from somewhere I don’t know. I have a suspicion of the crank case ventilation valve malfunctioning.
I also have a few codes being thrown for insufficient air flow.
 

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2004 325i automagic
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Is that insufficient air flow code a p0411? If so that is for secondary air injection system, which only operates on startup and is peripheral to the engine.
 

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Discussion Starter · #9 ·
The current engine (I have just discovered) has a blown head gasket and an external radiator leak. The car is also running quite rich and has a rough idle (fluctuates between 500 and 1000 RPM) . In the past I also had trouble with acceleration, the engine would misfire under hard acceleration and felt like it essentially dies for a short period of time.
 

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Swap in another M54B25 or for a modest upgrade, or install an M54B30 as a plug an play swap.

You could also consider a head gasket job (or paying someone to do it), but an engine replacement is usually easier, less risky, and about the same $$.
 

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2002 330 Ci
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Swap in another M54B25 or for a modest upgrade, or install an M54B30 as a plug an play swap.

You could also consider a head gasket job (or paying someone to do it), but an engine replacement is usually easier, less risky, and about the same $$.
Finding a decent motor is an issue to though. But a swap is pretty easy after I've done mine.
 

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Discussion Starter · #12 ·
Swap in another M54B25 or for a modest upgrade, or install an M54B30 as a plug an play swap.

You could also consider a head gasket job (or paying someone to do it), but an engine replacement is usually easier, less risky, and about the same $$.
So thats why I had the idea to swap in a low mileage m54b22 that I have, I know its less power but it's what I have got. It's only got 97,000 km on it. So my only concern is the ECU, can I take the ECU from the m54b22 or does the ECU from the original car have to stay with the car and be reprogrammed?
 

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Original ECU to the car (M54B25) then you will flash it with the M54B22...It all sounds feasible, but there aren't many threads discussing this swap...Good luck. Let us know how it goes.
 
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