i recently noticed when i put car in sport mode and floor it i feel car bit shaking .. to me it seems like not enough fuel getting where it should be … similar symptom of injector problem on the diesel semi truck engine , check engine light goes on and when i stop at the stoplight right after car still shakes little bit.
i pulled over on the parking , turned engine off , started - no check engine light , i tried to floor it again (was not sure if something wrong with shifter programming , recently did SAT retrofit) - same situation , but after starting the car again check engine light is still on , today i tried to push little bit gas pedal at 30-40mph in regular D - shaking
stopped at auto zone just to check the code : p0303 (not sure if this is bmw code from auto zone keychain scanner )
cylinder 3 misfire :
causes
a. plugged of faulty fuel injector
b. vacuum leak
c. engine mechanical condition
i am at 59xxx miles , any ideas ?
mechanic said he used to have 335i with same problem , that time it was injector , he used 3 times techron injector cleaner and the problem was gone … not sure where to start.
thanks

 

Did you replace the plugs at the regular service interval of 45-50k? If you did then swap coils to make sure it's not the coil. If the misfire stays on cyl 3 then that injector is bad and that bank will need to be replaced. Definitely not a vacuum line issue. Gut tells me its a injector.

 

did not change plugs yet , got car at 50k .. will try this first

 

Try plugs and coils. Had similar issue on mine. I replaced all plugs, and replaced cylinder 1 coil, all is good now.

 

I have had the same problem, first i changed the spark plugs to different cylinders, if the code appeared on a different cylinder, then the spark plugs are bad. Then again you can hear if the injectors are bad.

 

Don't buy a coil until you confirm its bad. I had same problem and it was only a plug. While I was in there I swapped the coil with anothr one and if the coil was bad the problem would have moved. It didn't so plugs were the culprit.

 

replaced plugs today and coil number 3 - fixed the issue
i was pissed of the fact that i need 14mm 12 point socket to get plugs out … not even regular one but thin walled or 14mm 12 point spark plug key , i spent 1 hour today finding this key , not in any auto store , not in sears … later on my friend mechanic brought it for me to do the job , before i changed the plugs i put new coil on cylinder 3 and this fixed the issue right away , since everything was ready for the plugs - i did this too.
thanks again guys

 

regular deep 14mm 12 point socket from advanced parts did not work , too thick

 

Good to see it was a easy fix.

 

unfortunately i am not that lucky … today i got misfire on cylinder 5 … almost same symptoms