Dear Customer my apologies for the delay, How the fault occurs the time had to have been left with a tooth out of place I do not think it is an external problem becasue it happened right after the repair of the time chain and they also have the exact symptoms of a problem in the distribution, if the technician considers that the time is right and if he has tried to accommodate it On several occasions and the problem is not corrected I will recommend that you locate another technician take the time and distribution of this engine is not so easy like the other BMW
Dear customer anyway, check the advance of the injection pump, because if this is the problem, this fault appears, but you should check the distribution for this anyway.
Also dear customer, I am concerned that the technician has taken the distribution time wrong and then has corrected, it becasue if in the first ignition it have extrusion time incorrectly the combustion chamber or cylinder head suffers a defect and therefore never remains working correctly even when they then correct the distribution time.
I do not want to doubt the technician who made the work nor his capacity, much less in the knowledge that he has but the most prudent at this moment would be to have an external technician give you a second opinion because I repeat that you have the exact symptoms of a problem in the distribution of the engine and in addition the characteristic that occurred just after taking the time distribution is what indicates that the problem is here.
Maybe the distribution chain is stressed by a problem in the tensioners, in a skate but already a technician should verify this.
Have you understood me dear customer?
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Best regards, Sebastian.