M54 Engine Management Woes !
Hi Guys, and thanks for the invaluable advice & experience. Awesome! I've owned a lovely, well-cared for, year 2000 Z3 2.2i (M54 B22) since March '12. With over 86k on the clock, it has a persistent problem, thought to do with the emissions control system, which effectively prevents me taking the motor over about 4,000 rpm some - but not all- of the time.
I've quickly discovered that there could be quite a large number of reasons for the ECU triggering a fault code and going into limp mode ! This even happened once on cold start-up. However, I often find that, once thoroughly warmed, the car will run perfectly, even with enthusiastic use of the gas pedal.
I'm gradually working through the usual suspects, and have so far changed oil, fuel filter/reg., air filter, plugs, and the rearmost rubber elbow (air intake) to the manifold, which had cracks. A new MAF was fitted early on as a knee-jerk reaction by a local mechanic (who billed me £300 and threw away the original Bosch part !)
This past weekend, I serviced the DISA valve using a new parts kit from the States (as a precaution really.) Great kit but what a fiddly job ! ( The old OE parts were in surprisingly good shape apart from the 'O' ring mounting seal.)
I also find it hard to believe that it may be due to a faulty coil-pack, but I've got a new one on standby....
The car always runs sweetly below 4k with smooth pick-up and lovely linear torque, and really comes alive at around 5k. I tried Raj's plastic bag test over the oil-filler, and it seems to suck at idle -quite a lot ! Do I take this to be a bad thing ?!
Sorry for prattling on at some length, but I would like to mention that there's an odd expansion/resonator/collector box just aft of the MAF sensor, attached to the bottom of the main air intake trunk. I say odd because it doesn't seem to show on BMW microfiche for my vehicle...
This type of engine would appear to be air-leak city with advancing age, but if any of this sounds horribly familar to anyone, please let me know before I lose any more hair !!