[Khan535i]

Alright guys I need some guidance here.

My 535i has extremely rough idling when initially cold starting. So bad to the point that sometimes it shuts down. The motor literally stalls and shuts off. Other times the rpms get so low to the point that it's about to shut off but the car somehow revs itself to a point where the car won't shut off.

While driving the car is fine, there might be a performance issue but I don't have anything to compare it to. Giving gas on first gear has been starting to need more to be able to roll off. (This could just need a throttle reset)

I get 3 codes. 2 are O2 sensor related because I have striaght pipes but no tune. The main issue is the MAF sensor code which might be the reason for the shutting down and rough idling.

Code: P00BD. I attached a picture of the description.

Will getting a STAGE 2 tune make the ECU regulate the fuel to air mixture ratio in the cylinders and be worth buying, or is this some other issue?

Thanks Guys.

[ctcarbonari]

I can't attest to the tune question; however, I can provide some insight on rough cold start issues that have worked for others & myself.

N55 Engine, only during cold starts

Symptom: Initial RPM dip down to ~500 followed by a correction rpm spike up to ~2000 then back down to ~1100 rpm where car goes continues thru the 42 secondish routine of blowing out the cats and slowly going back down to idle rpm (~700).

Months ago my 15' 535i started doing this intermittantly. Then eventually became an every cold start occurance. On two occasions, the initial rpm drop cause the engine to die and I had to restart.

There's quite a few posts out there on this topic with many different opinions on causes (spark plugs, ignition coils, fuel injectors, software, etc...).
Here's a very simple DIY that worked for me and a few others (where I learned from).

Solution:
While cold, disconnect the MAF sensor.
Cold start engine and let it idle for ~5 mins (I did mine for 10).
Shut engine down & reconnect MAF sensor.

I did this about 5 months ago and haven't had a single startup fluctuation since. (I also cleaned the MAF sensor w/ CRC spray as well but it really did not show signs of build up).

Not saying this will work in OP case, but well worth a try. Also, since the OP is already showing a MAF code there may be something else going on. It's worth cleaning & reconnecting. Also, clean out the pins on the connector. And again, it may be tune related in the OP's case.

That's just my experience with a stock N55.

Good Luck!

[Khan535i]

Thank you so much brother, I will try and let you know 👍

[ctcarbonari]

Originally Posted by Khan535i

Thank you so much brother, I will try and let you know 👍

You're welcome and please do (@ post back).

I've never been able to get a 100% straight answer as to why that works for some. I can only assume that there is some sort of "reset adaptations" type of software thing happening.

DO make sure you try it during a cold start (and not later in the day). Not sure if it matters but better to be on the conservative side.

I hope it's as simple as that for ya, but the error code makes me think you may have more going on (like possibly bad MAF sensor).
For me and others, this little startup glitch would never throw a code.

I'll be keeping a good thought for ya!

[Khan535i]

I know it's been a long time but it randomly came to my mind that I never replied to you.

To keep it short, it was a boost leak 😂

Got it fixed and the problem was gone, power increase was exponential, and the mpg got better.