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The 5th generation BMW 5 Series was produced from 2003 to 2010. For these models, BMW introduced a controversial new design, the iDrive control system, and active steering.

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I have a bmw 2007It consumes a lot of gasoline Anyone knowledgeable

hello i have a bmw 2007 My car used to have a 523i engine but I modified it to a 525i engine and after I changed it now consumes more gasoline than other bmw

how can i fix it.

Answer this question I have this problem too

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The two have completely different displacement options, so you can't just drop a 525 engine in a 523. The tune is optimized for the 523 engine (2.5L N52), not the 525 (can have a 2.5L or 3L N52) so the car is compensating for this by using more fuel because the ECU is adding fuel to compensate because the car thinks it doesn't have enough fuel due to this swap. See the issue? If you installed the 3L engine in a car tuned for a 2.5L, you WILL run into problems with the stock tune.

Ultimately you have 2 or 3 choices:

  • Reflash the ECU to match the 525i, making sure if you put the 3L N52 in you use a 3L tune (keeps the original ECU/immobilizer, and matched ECU mileage log if these ECUs track it in both the cluster and ECU) ($)
  • Replace the ECU for a 525i ECU (will create a mileage gap that shows when you check the dash if stored in the ECU+dash cluster, and you need a high-end Autel scanner to pair your old immobilizer; $$ or $$$ depending on if you pay a shop to do the swap and immobilizer pair or buy the tool)
    • IF you know how, it is possible to replace the ECU but you will need to pair your immobilizer to the new ECU; Autel sells a scan tool that does this, but it is EXPENSIVE. See: Autel IM508

The other option (if you want to do it) is to see if you can have a tuning shop remap the ECU. But be forewarned: this will trip a flag that's permanently set if the 2007 BMW ECUs do this. 2008+ BMWs are known to be encrypted AND trip when tuned and they cannot be reset without a new ECU. I would contact a few shops in your area if you have any; if not, see if you can do it with a Dinan tune or if it needs to be reflashed. I am not considering this an option "easy" because it's costly and will probably trip something.

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3 Comments:

Can you explain more please I really need help I am getting tired of my car.

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Nick is saying, your car computer does not know you have a different engine. So the car computer makes poor decisions of how much fuel to use.

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@nest2g Back in the days of carburetor engines you could put a 427 Hemi in a 389 stock car by tuning the air/fuel ratio, but since they went to fuel injection it wasn't done with a few test drives and a few hours in the garage. The only surefire way these days is to tune with the stock engine, or if you swap it over you need to have a shop put an aftermarket ECU in and tune that.

It probably requires a reflash to the 525 tune, especially if a 3L N52 was installed. Otherwise if you put a 2.5L 525 in a 523 these shipped as 2.5L N52 cars unless BMW made other changes which cause problems.

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