M50d cold start issue

[BMX5FN]

Hi,
Having an issue with cold start on 2013 m50d with 120km.
Starts dine and after 3-5 seconds drops up and down in revs and has a rough idle for 30-60 seconds or so, sounding like it's about to stall.
Seems to have a strong diesel smell as well outside the car. Once warms up the car runs perfect with no other issues throughout the day.

Only happens on first start up of the day after sitting at night.
Recent service and fuel filter change hasn't helped.

Car runs fine with no recent change in power or consumption.

Any thoughts or ideas ?
Thanks

[devlinsky]

Your injectors are dying and/or DPF is clogged. Check both.

In my case on of the injectors had to be replaced - didn't help - then I forced the DPF into regenerative mode - that helped a lot, but not 100%

Recently I was contacted by a fellow from Brazil with identical issue. His dealer diagnosed two dying injectors and since they are nowhere to be found there - he had them refurbished with great results.

However - according to my knowledge, there is no way to refurbish those injectors, so either there's something new on the market or - I have no clue. I tried to investigate - haven't heard from him since.

[BMX5FN]

That's for that, appreciate the feedback.
How did you force a dpf regen? Maybe worth a try before replacing injectors as I suspect not a cheap exercise.

No fault codes as well. Admittedly my wife mainly drives it and it's all stop start city driving. A dpf clean maybe worth a try.

[devlinsky]

I used Carly for that, I believe Ista can do it too, as many apps/obd2 tools. Helped a lot here. Also, I switched permanently to premium fuel, as indeed, injectors don't come cheap, to say the least.

Try to clean DPF - either by app or have it professionally cleaned - as it looks like a good path to follow and please report back with results.

[BMX5FN]

I will book in for a dpf clean and let you know. Thanks

[BMX5FN]

Have done dpf regen but only slight improvement.
Has been suggested to do a manifold clean as the next step. Swirl flaps not opening to their full extent.
Will have this done in the next few weeks

[devlinsky]

I did the manifold walnut blast sometime ago, when the whole issue started - no influence whatsoever. It might be injectors after all, sadly.

What was the regen procedure you did?

[BMX5FN]

Not sure, a bmw trained tech did it for me.
Defiantly running better after this, but still has cold start issue.
He did say re: injectors, cylinder 2 was using more fuel and may be issue? He will investigate this further with manifold off.
I'll go thru the process and let you know how I go.

[devlinsky]

Originally Posted by bm323in

Not sure, a bmw trained tech did it for me.
Defiantly running better after this, but still has cold start issue.
He did say re: injectors, cylinder 2 was using more fuel and may be issue? He will investigate this further with manifold off.
I'll go thru the process and let you know how I go.

If cylinder 2 used more fuel than other ones, then my guess is that something wrong with the injector.

Check around if anybody around offers injector reconditioning. There's a fellow from Brazil that contacted me with similar issue, BMW diagnosed faulty injectors but since new injectors are nowhere to be found, he was offered reconditioning - and he reported great results. Sadly, I couldn't get any other details from him (language barrier).

[P1]

Although I have a 35i, have had this happen to me also. Turned out to be a faulty injector. Replace it before it REALLY goes and leaves you stranded.

[BMX5FN]

The manifold clean seems to have fixed the issue.
Was extremely caked and the clean has fixed the cold start issue.

[devlinsky]

In my case the reason of cold start issue combined with "misfire" related symptoms was a faulty MAF sensor. After the sensor with the loom was replaced, all issues were gone. How was it diagnosed? Pull the MAF plug and see if that helps.

[Assassin]

A copy of a previous post elsewhere:

I've been driving 3.0l BMW diesels for 20 years and NEVER had a dpf clog. Its quite simple, no diesel with a dpf likes lots of short little journeys all the time. They thrive on being worked quite hard and periodic long journeys. The dpf regenerates automatically when certain criteria are met. It needs to be at running temperature and travelling consisently for a period of time and crucially must have a certain fuel level at the time. I can't remember the exact amount but probably over half a tank as the regen uses more fuel when operating and sometimes you see motor run a little warmer for a short period or hear the process completing when you park / switch off. This is all normal. I have tried fuel additives etc and them defintely help the engine sound a little less clackity but didn't seem to impact regens at all. Put simply these engines love a good workout and if you are worried about tickets etc simply drive a few miles on a journey in manual mode and keep the revs up a little. Garages will advise dpf cleaning etc to make extra $ all the time....... just give a periodic thrashing.... job done!