+ mine does that too, somedays i have a jerking effect useally when im cruising along at a pace and sometimes when i just top a hill and start to decline down the other side. jerk, jerk, hesitate jerk, then goes away.
THE GOOD NEWS = most likely not
NOT timing, ( or most likely just replace every 40,000mi.)
it may be the exhaust manifold...
it may be the air-intake needs cleaning
some of the ABOVE PROBLEM may be due to other things besides fuel and intake.
ive got the factory exhaust and when doing the HOT-SOAK i noticed some smoke coming from the exhaust manifold...
this indicates a major loss of power and perhaps the culprit of the jerking i have in all gears, with a full tank or empty and more often(i think) on days when the weather competes with BACKPRESSURE created by tiny hairline cracks in my manifold.
again if i had not ever done the hot-soak i would not have noticed the leak.
and since i did.
im now going with headers and a catback... anyone please help me find one ...
but your main problem could be a simple vacuum hose, that controls the fuel regulator , the air filter, a crack in any air intake housing (squeeze the big black hose in-between the airflow meter and the intake manifold --simple fix), also could be a
- loose ground wire
- poorly adjusted idle
- rotor, cap, wires,...... rotor, may have water in it
- fuel grade ... ...........higher or lower octane .. mine runs best on 87 oct.
- fuel filter
- fuel hoses,
- fuel gas cap,........... the seal may be old
- fuel pressure,
- fuel regulator ........ easy 10 minute-$65 dollar fix,
- vacuum hoses .. ...10 cents a foot, need one foot
- exhaust ...................back pressure
- catalitic converter,,,.. im counting the days for a cat-back system 300.00
i also pulled out the fuel pump and it was scary at first but really easy, i may buy a high end one because it will be a breaze to replace but the exhaust is first.
plus i heard i could get upto 30 more horsepower from the cat-back and headers.
anyways start with the cheap stuff and report here for great advice from the bmw fanatics.