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The vehicle has had repairs to its head gasket, timing chain, and guides. The Valvetronic motor, cam cap seats, injector, coil pack, and plug have been inspected.

Despite having completed all the necessary maintenance, there is still a persistent issue with cylinder 5, namely a misfire.

The vehicle starts well and operates without any issues. However, when I drive on the freeway, the vehicle's performance may be lacklustre and jerky, failing to provide sufficient power. Subsequently, the engine light illuminates without any prior indication, only the presence of the light.

The mechanic is disoriented and has exhausted all possible solutions. Furthermore, the compression of cylinder number 5 was checked and found to be satisfactory at the time it was performed. However, it has not been retested since.

Has anybody else encountered this problem? It is quite exasperating.

The vehicle in question is a 2007 325i.

Perhaps it would be advisable to limit the discussion to a single thread in order to prevent redundancy and bewilderment.

I intended to remove the other one due to the presence of more information, however I am unable to do so for an unknown reason.

Assistance is urgently needed.

Have you attempted to interchange the coil pack in order to see whether the malfunction has shifted to a different cylinder?
That would be my first course of action.

My technician has informed me that he has completed the task and will re-examine the timing.

Has he conducted a compression test, inspected the injector and wiring, and verified that the ECU is supplying power to the injector?

Furthermore, I conducted a compression test on cylinder number 5, which yielded satisfactory results at the time. However, I have not performed this test again subsequently.

The wiring has been fixed, and a new injector has been installed.

There is a possibility that the connecting rod is bent. If a sufficient amount of water enters the cylinder due to the blown head gasket, then I suppose it is plausible.