Sounds like a crankshaft sensor or camshaft sensor issue to me. :thumbsup

 

The noise may be blocked ccv system, try driving with the dipstick removed and see if it stops.

 

The only fault code reading is Generator communication fault.

The crankshaft or cam sensor fault (if it IS that) might not yet be recorded on the OBD as the revolutions are so few while the problem exists. In other words, the engine doesn't conk out completely, it stutters for about a second then drives as normal. So the OBD doesn't register it as a huge problem. yet.

If it is the crankshaft sensor this would also explain why the problem doesn't occur at speed, as it is turning so fast that the sensor literally hasnt got chance to kick in. Like an eye trying to pick out an Ace in a speedily flicked pack of cards. I hope my thoughts are making sense.

The garage have advised that for the moment, no harm will come to the engine by leaving it. They can't isolate the problem until it gets worse.

Intuitively to me I don't like leaving a problem, although I understand the logic. I'm concerned that by leaving it, it might cause a further problem to the Engine Management system. Can you provide any information on "generator communication fault" ?

 

Do you have any fault codes?

 

I asked for the fault code - I was told it was "generator communication fault" so I assume the code itself was 28D7 . This implies the alternator connections to the ECU are at fault?

Many thanks. its getting worse.
Mike

 

Garage has discovered that one of the cam sensors was full of oil. Not replaced it, just cleaned it out.

Also, that clutch assembly on the alternator itself was sticking. Could that be a cause?

Unfortunately since it was in garage yesterday, its developed separate fault which I think is too much of a coincidence to be anything other than connected with the work they've done. It's now revving up to 1500 intermittently whilst idling. I'll open another thread.

 

Did they change the o-ring on the cam sensor? If not it'll fill up with oil again.

 

I said I'd update this, for the benefit of others having same problem. It seems to be common for the n42.

Car taken to BMW specialist who found "lots of codes" (don't know what they are yet) and wiped them doing a software reset. Fitted a new clutch assembly within the alternator, the old one was totally knackered apparently. The idle surging throttle problem gone, but that was not the original problem anyway.

After getting back from garage it drove beautifully for 3 days then...

Unfortunately, the problem still there, and now worse, as it cut out doing 70mph while cruise control on for a second. Quite worrying. In total, it cut out, as above, with battery light coming on with what feels like a massive misfire etc, four times within half an hour. The last time it cut out, at the same time there was a beep from the dash, then the yellow ASC warning light came on together with the brake warning light (the one furthest left on the indicators on the right hand side). These indicators stayed on until it was safe to park the car up for a few minutes. Then all seemed fine.

Back to garage next week, still hoping its a sensor, though I'm told if it was, then it would have thrown an appropriate fault code.

Thanks fellas
Mike

 

Crankshaft sensor from BMW, not cheap, fitted. Running fine now - done about 150 miles since work done. (Hope I dont have to post again to this thread in a few days time!!)

 

Bang on

Yep my 1st e46 coupe with n42 done exactly the same thing. id be driving along when from no where car could cut out along with eml lamp on and tsc light on. only difference is mine always showed a crank and cam sensor fault code. Alls well that ends well thought crank sensor pita to replace unless you remove inlet manifold !!!

 

sorted

Exactly same symptoms as I had, started just blinking battery light then progressed to cutting out completely. Once it had cut out I bet it wouldnt start up, yet leave it 3-5 minutes and it starts fine with all error lights gone.

I too changed crankshaft sensor and cam sensor and not had any further problems for about 4k miles.

Common fault on this engine, problem solved now so put it behind you and enjoy your bm worry free!!!!