pegaki
Member
last month i started to experience rough idle (aka vibration at idle) problem with my E90
symptom:
the car will start to vibrate when stop at traffic light, usually 3~5min after cold start, at low frequency (ie not the high frequency vibrations that you would experience due to weaken engine mounting)
you dont feel the vibration when the car is moving, the vibrations are felt only when stop at traffic light (D, P or N)
the vibration is mild at D, but the strength of the vibrations increase significantly when shift from D to P or N , and is strong enough to feel it on the car seat and floor board
at P or N, the rpm needle will also fluctuate +/-50rpm about 800rpm (unstable rpm needle) when these vibrations happen (the rpm needle does not fluctuate when brake at D)
suspect:
initially i thought was due to damaged ignition coil or spark plug
actual cause:
upon OBD diagnosis, it turn out to be faulty air intake MAP sensor (air intake MAnifold Pressure sensor)
cost $120 to replace (labor+part), now the vibration and fluctuating rpm is gone!
symptom:
the car will start to vibrate when stop at traffic light, usually 3~5min after cold start, at low frequency (ie not the high frequency vibrations that you would experience due to weaken engine mounting)
you dont feel the vibration when the car is moving, the vibrations are felt only when stop at traffic light (D, P or N)
the vibration is mild at D, but the strength of the vibrations increase significantly when shift from D to P or N , and is strong enough to feel it on the car seat and floor board
at P or N, the rpm needle will also fluctuate +/-50rpm about 800rpm (unstable rpm needle) when these vibrations happen (the rpm needle does not fluctuate when brake at D)
suspect:
initially i thought was due to damaged ignition coil or spark plug
actual cause:
upon OBD diagnosis, it turn out to be faulty air intake MAP sensor (air intake MAnifold Pressure sensor)
cost $120 to replace (labor+part), now the vibration and fluctuating rpm is gone!
