This morning, I read a piece of news reading as: one BMW owner drove his car to the garage for repair because his BMW has abnormal noise engine. Then the repairman thought the air compressor had trouble and changed his air compressor. Besides, some more repair and maintenance are also included: engine, replaced the belt, cleaned the fuel system and air intake system, modified water system, and replaced the tank and oil, and the garage charge him 2517.5USD in total. But the engine still had abnormal noise; the BMW owner was annoyed and took this garage to the court.
Then how to troubleshoot the abnormal sound from your automobile?
Firstly, you need to have the basic knowledge that BMW engines tend to be louder at idle than other car brands, especially the straight 6 petrols, the latest N20 2.0i turbo is an example of the latest engines having a diesel like idle.
If the noise is abnormal, what to do?
According to my experience, I share some tips what I know here:
Basically your oxygen sensor is getting an abnormal reading. The abnormal reading will result in the sensor being unable to adapt beyond its +/- 10% threshold to adapt for the fuel/trim mixture. Therefore, either your car is going to run too lean (not enough fuel) or too rich (too much fuel).
Problems: 1) Either your pre-cats oxygen sensors are bad. 2) Fuel pressure regulator 3) Leak in the air intake /vacuum system I would think that it is probably your oxygen sensors. Replace that and you should be good to go.
But if the noise is produced by the fault ECU and the engine fault light abnormal light, then diagnosis with BMW ICOM, I used to have the same problem and I got one BMW ICOM from uobdii.com shop, then the problem was troubleshoot. BMW ICOM helps read and clear the trouble codes stored in the ECU and reset the ECU troubles, then you will not hear the abnormal noise from engine.
Wish what I share will help you if you have the same problems.