[a11y]

This relates to my 2007/57 pre-facelift N52 330i.

Last weekend (on the way home from hospital after the birth of my daughter, of all the bad times for it to happen...) I got a LOT of grey/black smoke from the exhaust under hard acceleration, with the smoke continuing after lifting off. Smoke also present on start up from cold and from warm. And we're talking a LOT of smoke: enough to totally obscure the car you've just overtaken . Oil level is fine, coolant level perfect, nothing untoward under the oil filler cap. Lots of black bits on the rear of the car (like the particles you'd get from a diesel) and exhaust itself is very black. Performance is reduced - just doesn't feel like full power, with the occasional stutter/misfire. I've tried a treatment of Redex injector cleaner but no difference.

This morning I took it to a recommended auto electrician/mechanic. No codes were brought up on the fault reader initially. Mechanic took it from a drive with me in the car - after hard acceleration off a roundabout his exact words were, "Oh ya f**ker* as he looked at the amount of smoke behind the car...

Got back to garage, disconnected the MAF sensor (aka air flow meter) and went for another drive: no smoke whatsoever and decent - although possibly not full - performance. Stopped in a layby, reconnected the MAF sensor, and as soon as we drove off an engine management light came on, smoke reappeared from the exhaust, and the car was incredibly hesitant and running poorly. Fault reader diagnosed a problem with combustion in cylinder 5, no other fault codes reported.

We're all a bit unsure where to start so looking for ideas/opinions...

It's definitely running rich - burning too much fuel.
Injector(s)?
O2 sensor(s)?

Initially he's going to replace the MAF sensor for starters, but if that doesn't solve it does anyone have any good/sensible suggestions?

Cheers,
Ally

[doughboy]

1st off congrats on the baby, all well I hope.

Must be your second if you're finding time to worry about the car....

Sounds like overfueling. needs a bit more digging, do you have an oiled air filter?

[a11y]

Originally Posted by doughboy

1st off congrats on the baby, all well I hope.

Must be your second if you're finding time to worry about the car....

Sounds like overfueling. needs a bit more digging, do you have an oiled air filter?

Cheers . All well now but wife had a 'mare of a labour ending in emergency cesarean...

Nope, it's our first - still enjoying a few days "off" on annual leave, hence finding a bit of time to have this looked at.

Car totally standard mechanically so just the OEM filter in there.

Just waiting to hear back from the mechanic but he'll not have the MAF til early next week. I could be off the mark but to me it seems obvious there's an issue with the MAF but I'm concerned there's going to be more to it, just have a bad feeling.

[Three_thirty_I]

Just curious to know if you eventually got this sorted out??

[a11y]

To the best of my knowledge, yes.

I left the car with the auto electricians all week and they were unable to replicate the fault following the initial reoccurence with them described in my initial post. All the did was unplug various electrical connectors, clean up contacts if there was any hint of moisture/dirt, and reconnect.

Car has ran perfectly ever since with no reoccurence and still no fault codes.

[Three_thirty_I]

Originally Posted by a11y

To the best of my knowledge, yes.

I left the car with the auto electricians all week and they were unable to replicate the fault following the initial reoccurence with them described in my initial post. All the did was unplug various electrical connectors, clean up contacts if there was any hint of moisture/dirt, and reconnect.

Car has ran perfectly ever since with no reoccurence and still no fault codes.

That's weird! Well disconnecting the MAF puts the ECU into factory running mode, so maybe in a way it forced the adaptations to relearn after everything was reconnected with the cleaned connectors.

Glad that you got it sorted out!

And congrats of course!!

[a11y]

Originally Posted by Three_thirty_I

That's weird! Well disconnecting the MAF puts the ECU into factory running mode, so maybe in a way it forced the adaptations to relearn after everything was reconnected with the cleaned connectors.

Glad that you got it sorted out!

And congrats of course!!

Thank you! Seems bloody ages ago now, had some seriously long, relatively sleepless nights since