[roadslug]

So our 2015 is riding the struggle bus right now. My wife was complaining the car would hesitate after the cold morning start. I confirmed and note once you get it above idle it clears up and then seemingly just goes away. Fire up later in the day, no problem.

It did throw the lean codes 118401 and 118001

I did spray starter fluid around and didn't notice any real change in RPM.

PCV system or intake tube? The charge pipe/FMIC is aftermarket.

[roadslug]

Other clues - The car was doing this a month ago. I changed plugs and coils since it's at ~60k. In doing so I found the ignition/injector harness had some insulation chewed around cylinder 3. BMW replaced the harness a few days ago. Perhaps the injector shorted and was damaged? I would think that would cause an issue all the time, not intermittent.

I just jacked the car up and took a look at the following:

Down pipe - tight, no signs of exhaust leak

hot side charge pipe - tight, no signs of damage

cold side - tight no signs of issues

air inlet tube - looks ok, but it sure is burried

oil fill cap - some oil build up below it. maybe...but the large deviation code seems something bigger

valve cover - no obvious signs of leaks

[BMWILUVU]

Probably vacuum leak

[roadslug]

another clue

Also pulled a code for intake air temperature shorted to +12V

ISTA says step one to fix the MAF. My understanding intake air temp comes from the MAF

So I data logged tonight and noted the following from BM3

1) IAT shows normal. I also heard IAT could come from various sensors. Not sure which one BM3 uses

2) When it is in "hesitation" mode AFR is stuck at ~19:1, no osolating, nothing. Cruising speed it seems ok but still shows lean. Give it a few minutes of driving and AFR starts responding normally and the car drives like nothing ever happened.

[thejeremyman9]

Originally Posted by roadslug

another clue

Also pulled a code for intake air temperature shorted to +12V

ISTA says step one to fix the MAF. My understanding intake air temp comes from the MAF

So I data logged tonight and noted the following from BM3

1) IAT shows normal. I also heard IAT could come from various sensors. Not sure which one BM3 uses

2) When it is in "hesitation" mode AFR is stuck at ~19:1, no osolating, nothing. Cruising speed it seems ok but still shows lean. Give it a few minutes of driving and AFR starts responding normally and the car drives like nothing ever happened.

IAT in datalogs is not from the MAF, its from the MAP, and the one on the charge pipe if i recall correctly, but would need to confirm its not the intake manifold MAP. If you posted the actual full codes with the description as pulled from the code read that would be helpful. Also post the data logs...

If the AFR is not moving then you have an O2, wiring, or software issue. The software issue being the least likely. A "tired" O2 can give symptoms like that.

[roadslug]

To follow up

O2 reading 19:1 warming up. This is normal until the sensor warms up.
I replaced the IAT sensor located within the MAF which it eventually threw a code for

Problemo solved.

[thejeremyman9]

Originally Posted by roadslug

To follow up

O2 reading 19:1 warming up. This is normal until the sensor warms up.
I replaced the IAT sensor located within the MAF which it eventually threw a code for

Problemo solved.

What do you mean "the IAT sensor located within the MAF "?

[jziehr70]

I have an 2013 bmw 335xi m performance with a cold air intake and just recently the car has started to lurch when under load around half thorttle and have a loud whistle sound it isn't having any codes pop up ethier it doesn't do it if it's not under load or anything and it's not a huge lurch but u can feel it's struggling and if I put it to the floor the car seems to feel gutless if anyone has any ideas on what this would be would be nice thank you

[n55david]

Originally Posted by thejeremyman9

What do you mean "the IAT sensor located within the MAF "?

There is one in the maf. Thats where ambient comes from I believe.

[thejeremyman9]

Originally Posted by n55david

There is one in the maf. Thats where ambient comes from I believe.

I am not 100% sure on that part but was mostly wondering how he would replace a IAT sensor within the MAF lol

[n55david]

Originally Posted by thejeremyman9

I am not 100% sure on that part but was mostly wondering how he would replace a IAT sensor within the MAF lol

Ahh lol yeah, have to replace the whole thing.

[thejeremyman9]

Originally Posted by jziehr70

Since I have removed my tune and put the car back to stock it has seems to get horrible gas mileage and now when I get into trying to merge onto the highway or anything it seems to cut power and jerk me forward and there's no codes and no engine light and now I have no idea feels like I'm running around in circles now it seems like it cuts power for a quick second and jerks and then gets back in it

What does that have to do with this thread? You already posted that somewhere else