pavrom

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

Booyaazaa

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.

pavrom

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

Kidduce

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

sidorsinigur

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.

tonyb635

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.

pavrom

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

pavrom

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

Booyaazaa

Good to see it was a easy fix.

pavrom

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