Cold rough idle

[Bmm34]

Hello, I'm a new member to the forum. I'm on my 2nd BMW. First was a 2009 335I and now I have a 2018 x5 35d.

About two months ago I started to have some rough idle issues mostly on a cold start but sometimes even when it was warm. The RPMs would fluctuate when I first start it up. It's progressively gotten worse and in the last month it has actually stalled a few times and the rough idle is more severe when it happens. I've noticed it happens more often when I back out of my driveway vs driving out, but it doesn't do it on every cold start.

I've had the steering module replaced under warranty and was told by the BMW dealership that that could potentially rectify the issue. They didn't see any other faults when doing a diagnostics.

Unfortunately the rough idle has persisted and so I was hopeful it might be the EGR causing the issue. I had a new one on order to be replaced under warranty. The EGR was replaced today and after I got it home and it sat for a bit, I took it out and it the rough idle happened again. The dealership can not replicate the issue.

Any advice would be appreciated. If I'm leaving out pertinent information, please let me know.

62,000km

Thanks

[devlinsky]

Your injectors are dying.

You need to leave the car at the dealership overnight and have them check for the injector corrections at the cold start. Then replace the injector or injectors depending on your warranty or piggy bank status.

[AmalfiCoast718]

Vacuum leaks will also cause rough idle issues. You can monitor your fuel trims with a scanner and/or perform a smoke test. Let us know what you find.

[Bmm34]

Originally Posted by devlinsky

Your injectors are dying.

You need to leave the car at the dealership overnight and have them check for the injector corrections at the cold start. Then replace the injector or injectors depending on your warranty or piggy bank status.

Thanks for your reply. What am I looking at for injector replacements?

Frustrating part is, I had it serviced just prior to the warranty running out and mentioned the issue.

[Bmm34]

Originally Posted by AmalfiCoast718

Vacuum leaks will also cause rough idle issues. You can monitor your fuel trims with a scanner and/or perform a smoke test. Let us know what you find.

Thanks for your reply as well. I will report back once I have more information.

[devlinsky]

Originally Posted by Bmm34

Thanks for your reply. What am I looking at for injector replacements?

Frustrating part is, I had it serviced just prior to the warranty running out and mentioned the issue.

In my case (M50d) one injector is around $1k plus labour. Six pots, six injectors. Simple math.

Chase them regarding the warranty. Ask for goodwill etc. Fight.

[RED_Y_]

$1000 per injector? This is crazy.

[devlinsky]

Originally Posted by RED_Y_

$1000 per injector? This is crazy.

#bmwperformancelife 😂

[RED_Y_]

Does M50d has some special injectors? Injector for US spec N57 engine is $350-400.

[devlinsky]

Originally Posted by RED_Y_

Does M50d has some special injectors? Injector for US spec N57 engine is $350-400.

Yes Sir! Those injectors are unique to M50d engines, they are so rare, that Bosch never released any service bulletins for them, so no shop can test, diagnose or repair any part of them. Error or correction beyond certain level - replace. At some point there were around 200 of them available for the whole Europe. Imagine that.

[RED_Y_]

Originally Posted by devlinsky

Yes Sir! Those injectors are unique to M50d engines, they are so rare, that Bosch never released any service bulletins for them, so no shop can test, diagnose or repair any part of them. Error or correction beyond certain level - replace. At some point there were around 200 of them available for the whole Europe. Imagine that.

I did not know that, wow this is very steep pricing. I bet its fun drive but sounds like not fun to maintain.

[XxBBVTMxX]

I think this is normal, especially if your vehicle is cold. Does it feel normal after the engine warms up?

Mine does it very lightly until it gets to operating temp. I have all new injectors, CBU done at 100K, all new seals, etc. Currently sitting at 118K+

[Bmm34]

Originally Posted by XxBBVTMxX

I think this is normal, especially if your vehicle is cold. Does it feel normal after the engine warms up?

Mine does it very lightly until it gets to operating temp. I have all new injectors, CBU done at 100K, all new seals, etc. Currently sitting at 118K+

The dealership is supposed to get me a full report today. I left the car there all day yesterday and they wanted to keep it another day. Just before the service department closed, they said the intake manifold was full of carbon and might need to be replaced. Rough estimate $3500, but they would come back to me with a proposal.

I'll obviously say the issue has been there for awhile and I've had it in the dealership a few times times and they failed to properly diagnose it. Is there anything specifically I should be asking them or pushing for? I read on another forum that a damaged EGR valve (which was just replaced under a recall) could be a contributor.

Any insight anyone wishes to share would be appreciated.

Thanks

[AmalfiCoast718]

Did you read the codes and get fuel trim data? I have solved these problems on my 2003 e46 using excellent threads from e46fanatics, a live data scan tool, and a homemade smoke test machine. Intake manifold full of carbon sounds like a money grab from the dealer. Ask them to read any codes and look at short and long term fuel trim values. Or you can do it yourself with a scan tool.

[AmalfiCoast718]

Read this:

https://www.e46fanatics.com/threads/...50-fix.897616/

The engines in the X5 and e46 are very similar.

[Clifton]

How many miles on the fuel filter? Less than 20k miles? Any possibility of contaminated fuel?

[XxBBVTMxX]

Originally Posted by Bmm34

The dealership is supposed to get me a full report today. I left the car there all day yesterday and they wanted to keep it another day. Just before the service department closed, they said the intake manifold was full of carbon and might need to be replaced. Rough estimate $3500, but they would come back to me with a proposal.

I'll obviously say the issue has been there for awhile and I've had it in the dealership a few times times and they failed to properly diagnose it. Is there anything specifically I should be asking them or pushing for? I read on another forum that a damaged EGR valve (which was just replaced under a recall) could be a contributor.

Any insight anyone wishes to share would be appreciated.

Thanks

First thing I would do is read the codes to see what exactly is going on…

You can easily check the EGR valve, just remove the plastic back cover and push on it.. it it goes down easily and comes back up freely then it should be operating fine. You should get a code if there is an electrical issue on it.

As far as Manifold full of carbon… dude, just take it apart yourself and clean the crap out of it… by the time you make it to 100K it'll all be caked up in there anyway.. that's normal tear and wear 🤷🏽… look in the forums here, I believe others have put information on how to do it to include myself (been a hot minute)

I will say that to own a 35d, you really need to get in the habit of doing your own maintenance unless you got heavy pockets.

Also, I am pretty savy with CBU now that I did my own on manifold and intake ports 🙌🏽

Preferred scan tools would be the Foxwell 530 and ISTA+