RPM Drop at Startup

[Mojo85]

When I turn the car ON after a full night of being off, I sometimes have a weird RPM drop followed by an increase before idling at the normal cold start rpm range.

Typically on a cold start, the idle rests at ~1300rpm then drops after 20 seconds or so to below 1000rpm, approx ~800rpm.

But sometimes on start, the idle drops to ~600-700 rpm after turning ON then quickly revs to 1800rpm before dropping back to 1300rpm. Its as if some anti-stall feature is kicking in for a few seconds.

It used to happen every once in a while, but now happening more frequently. Anyone have any idea on what that might be?

[turboawd]

I'd start by cleaning the maf sensor. Then check for any intake leaks.

[IlliniX5]

Had the same issue with my ‘15 35i. Changed coils and plugs (86,000 miles, 2nd owner, not sure if they were original...) and now my start up idle is consistent. No more rpm surge or drop.

[P1]

Had the same on my 2015. Ended up being a bad fuel injector.

[scotty339]

Have you pulled/looked for any codes with a BMW capable reader?
How many KM on the vehicle?

If you have ruled out bad gas and a clean air filter.. Then I'd clean the MAF, then if still persisting I would do coils/plugs. If it still persists, Id look at your injectors. After that, vacuum lines. Mileage will dictate.

[Mojo85]

Originally Posted by scotty339

Have you pulled/looked for any codes with a BMW capable reader?
How many KM on the vehicle?

If you have ruled out bad gas and a clean air filter.. Then I'd clean the MAF, then if still persisting I would do coils/plugs. If it still persists, Id look at your injectors. After that, vacuum lines. Mileage will dictate.

54K Miles. I do think this happens more often when it is colder outside.

Issue been happening across multiple fuel tanks. All gas stations I go to are Top Tier gas. I’ll add fuel additive or switch to Shell V-Power for a while to see if that helps.

Plugs were changed at my last BMW service but this issue occurred a few times before that. Don’t think coils were changed.

So what I will do is:
- Check codes
- Clean MAF
- Check/Replace Air Filter
- Fuel assistive or Shell V-Power with an Italian tune up.

[scotty339]

Originally Posted by Mojo85

54K Miles. I do think this happens more often when it is colder outside.

Issue been happening across multiple fuel tanks. All gas stations I go to are Top Tier gas. I’ll add fuel additive or switch to Shell V-Power for a while to see if that helps.

Plugs were changed at my last BMW service but this issue occurred a few times before that. Don’t think coils were changed.

So what I will do is:
- Check codes
- Clean MAF
- Check/Replace Air Filter
- Fuel assistive or Shell V-Power with an Italian tune up.

Okay, so not high high mileage. In my eyes, you get about 60K KM from a set of plugs and 120K KM from a set of coils... two plug changes per set of coils. (or roughly 40k Miles / 80K Miles)

At this point I would not go out spending the money on coils until you check the other things mentioned.

If you need a good BMW tool, Carly/BimmerLink with a Bluetooth Dongle Adapter will set you back about $40 USD and can check what you need and much more.

Good plan. Report back with findings and we can go from there.

Cheers.

[turboawd]

What engine? The v8 can sometimes crack the intake pipes.

[Megatr0n]

This is happening to me currently. For some people when they changed the spark plugs, the fuel injectors, or the battery it stops but for other people like me it doesn't stops. This does happen more frequently when it's cold outside. I have never got a code from this and when I plug it in to a code reader I get no codes back. What has helped me lower how frequent this happens is I put the car accessory mode which is just pressing the start engine button without my foot on the brake, turn off the air conditioner/heater, I would wait around 10-15 seconds then I start the car. I have also closed the moonroof completely and this has also worked, I noticed that when I left the X5 over night with the roof cover pull all the way back, when I came in the morning I would see that the X5 by itself would start closing it but never fully.

I have also noticed that when I drive more than 30 miles everyday it doesn't happen. But when I drive very low miles during the week it does happen more frequently or when I don't turn on the car for a few days. Hope this helps and if you do find the solution, please let me know.

[hanggaw]

This is also happening to my car. It only happens when I turn it on the first time in the morning. The weather doesn't make a difference. After work in the afternoon, it doesn't do it. It started happening at around the 70k miles mark. Subscribing to this thread.

[michaelmack]

Same issue with my 2015 F15. Started around 65K. No codes, so might be time for some maintenance.

[ajob]

Originally Posted by michaelmack

Same issue with my 2015 F15. Started around 65K. No codes, so might be time for some maintenance.

My 2015 F85, 120K km, keeps doing this from time to time.

Maybe it is due to the occasional bad fuel, or maybe not, I have not found any good reason for it.

In any case, I just stopped worrying about it, as the roughness lasts only a few seconds after a cold engine start and then the engine always runs smoothly.

[Mojo85]

Update:

I used chevron fuel injector cleaner for 2 tanks of gas. I also replaced the air filter, it wasn't really super dirty and I am replacing it at 15K Miles mark. (1.5 oil changes ago).

The issue SEEMED to be gone initially in the first 3 weeks and the rpm drop wasn't occurring but then I started to see a *slight* sudden RPM drop for a brief moment. After 2 months, the RPM drop seems to be back, albeit not as bad as before.

I don't think the fuel injector initially solved the issue since the RPM stopped immediately after filter was replaced. In other words, I doubt the fuel cleaner did anything that fast.

Today I will be cleaning the MAF sensor. Again, there is no codes being thrown. My car is a sDrive35i.

[phipark]

Could be injectors or needs a valve cleaning if coils and plugs don't solve it.

[CeeTeeX5]

My wifes X1 had a similar issue and it was the tank vent valve that needed to be replaced. It would idle low right after startup and if you put it in to gear too soon after, it would stall. The X1 did have a CEL when this happened. Have you checked for any codes?

[turboawd]

Originally Posted by CeeTeeX5

My wifes X1 had a similar issue and it was the tank vent valve that needed to be replaced. It would idle low right after startup and if you put it in to gear too soon after, it would stall. The X1 did have a CEL when this happened. Have you checked for any codes?

Strange. My x5 started normal today but check engine light came on today.
Code 195014
diferential pressure sensor,tank vent valve, signal

Cleared and hasn't come back today yet. Seems like an easy part to change if this becomes a problem.

[Mojo85]

Originally Posted by turboawd

Strange. My x5 started normal today but check engine light came on today.
Code 195014
diferential pressure sensor,tank vent valve, signal

Cleared and hasn't come back today yet. Seems like an easy part to change if this becomes a problem.

I don’t have a code reader. Is this a stored code or a check engine light that comes up?

Cleaning the MAF sensor did not help this issue.

[crystalworks]

You just about need a good BMW specific code reader to own a modern BMW. And that's just so you can keep the dealership honest if you don't do your own work.

Carly works well for the F15. Helped me diagnose a couple of failing injectors on our diesel. But, there are better options. I have a hard time recommending Carly since they switched to their subscription based payment model. I'm grandfather'd in as an OG customer.

Other than that, I use a Foxwell NT520pro for my other BMWs. For the F15 though I believe you have to order the new NT530pro as the former won't work with the F chassis Bimmers.

[X5Guy]

Any updates with this issue? I've been having this issue for awhile also. Happens almost everytime during cold start in the morning.

[RED_Y_]

Originally Posted by X5Guy

Any updates with this issue? I've been having this issue for awhile also. Happens almost everytime during cold start in the morning.

Did you read thread? Which engine do you have? Different things can cause this, try ISTA may be?

[devlinsky]

It would be MASSIVELY helpful if you guys would add to your posts info like:

- engine
- fuel (petrol or diesel)
- mileage

Thank you