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Discussion Starter · #1 ·
Hello,

I have a problem with my bmw 750li n63b44 engine. I have dtc : 140601 (P0306) Misfires, cylinder 6: injection is switched off. I switched spark plug, ignition coil and injector with cylinder 7 but the dtc rest still in cylinder 6. I have 8 bars pressure at all cylinders. The cylinder 6 receive electricity. I don't know what i need to test now. Sorry for my english i am french ;)

Thank
 

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I have 8 bars pressure at all cylinders.
Looking at other N63 compression test results, you should expect around 12 bars of compression. Carbon buildup can cause loss of compression, especially if all cylinders are equally low, so that's something to check.

Removing the intake plenum is not easy on the N63, so instead of trying to inspect the valves with a borescope, use a can of something like CRC GDI intake cleaner and see if that makes any difference. Spray it just past the MAF like this:

 

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Discussion Starter · #4 ·
I changed the gaskets of the turbo manifold 2 months ago because an exhaust smell entered the car when the windows went down but that did not solve the problem. but at that time I had seen that the valves were really very clean no carbon.
 

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Thanks for your reply Robin. I'll do another compression test. maybe the engine wasn't hot enough?
Yes, it needs to be done at operating temperature. Below are the instructions from the N63 bulletin in the US. If you have ISTA, there is a test procedure that will crank the engine for you.

Font Screenshot Number Document



I changed the gaskets of the turbo manifold 2 months ago because an exhaust smell entered the car when the windows went down but that did not solve the problem. but at that time I had seen that the valves were really very clean no carbon.
That's the exhaust manifold at the top of the engine and not the intake plenum at the bottom, right?
 

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Discussion Starter · #6 ·
Yes the exhaust manifold at the top of the engine. I think in this engine for removing plenum it's better to remove engine. I don't have ista. Where do you buy your ista ?
 

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Yes the exhaust manifold at the top of the engine. I think in this engine for removing plenum it's better to remove engine.
It's the intake valves that get carbon buildup, try the intake cleaner and see if it makes any difference. If the buildup is severe, you may need to have walnut blasting done.

I don't have ista. Where do you buy your ista ?
Most resellers aren't authorized, so I wouldn't recommend buying it. You can download 4.32.15 from the thread below, don't use any version newer than that.

 

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Discussion Starter · #9 ·
I come to the news. A friend told me that the problem could come from the ecu and he sent me an ecu from a bmw 550i with the key and also the case 4 module. it didn't solve my problem so i put my ecu + cas4 module back but now i have lots of dtcs that appear when i start up lots of things don't work anymore. I took the car to the repairer he emptied the fuel in the tank now it is working properly. he also took the engine compressions and he told me that he found 12.5 bars everywhere, so my measuring device must have been faulty. now the car drives fine but a lot of electronics don't work anymore.
 

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the speedometer don't works, the gearbox remains stuck in normal D mode (no more sport mode, comfort...) no more cruise control, abs error, power steering, airbag...
Need the BMW specific fault codes otherwise it's just a guessing game.

I don't think it was a good idea to swap the DME and CAS...you may have triggered tamper protection. Check the coding board for more information on how DME or CAS should be replaced/reprogrammed.
 
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