Cold Start Log

[KevinC39]

I'm having a little cold start issue. It starts up fine, immediately stumbles and dies unless you tickle the throttle two or three times and then everything is fine. It drives fine and any warm starts after that are completely normal.

I'm not the best log reader so I figured I'd share or maybe some of you have ran into this before and could point me in a direction to look. I can't figure out the new way of getting the log to show up in the post unfortunately. I apologize. Thanks

 

[Mterkait]

Do you have cold start delete?
Check if there is any leak around intake.
Try stock Intake.

I had bad cold starts on my F30 N55 with BMS intake.

 

[KevinC39]

I do have cold start turned off and have a BMS intake but those have been there for over 2 years with no issues. I'll give it a look over for any leaks or loose electrical connections.

I was even wondering if it could be a dirty MAF or bad O2 sensor. I did reflash the tune last night just for the heck of it so I'll drive it around a little and see what codes I can pull from it. Nothing pops up on the dash.

 

[e92_n55_]

Could be a few things.
- Hpfp
- maf sensor
- injectors
- spark plugs/coil packs

Did you try flashing back to stock?

 

[KevinC39]

No, I don't have a stock turbo but I did reflash the same custom map that has been on it since last fall. I've driven it around a couple days now and it actually seemed to do pretty well this morning. Just a slight stumble and only needed to give it a little throttle one time. I scanned for codes after starting it yesterday morning and nothing showed up so I'm kinda stumped at this point. I don't see anything out of place either. Everything seems tight and connected. I guess It seems to be working itself out but something must be going bad for it to start doing it out of no where so I'll keep checking for codes and different things.

 

[Mikehalim]

I’ve been having coldstart issues on my E92 N55 since I got it... every winter it stumbles and dies and then is fine. Once the weather gets warmer 0 issues...

New plugs, coils, o2 sensors & injectors

 

[KevinC39]

I noticed I must have tightened down the oval shaped rubber accordion piece on the intake too much and crushed the tube going to the turbo. I replaced that thinking it might be an air leak causing my problem but nothing changed. Every now and then I'd also gotten code 387F power management: standby current violation. The battery was new in August 2016. I put the car on the battery tender over night and that didn't help either.

I still think it's some sort of fuel supply issue or a dirty/bad sensor. The LPFP is a Fuel-It stage 2 bucketed set up that was put in Fall of 2016. Obviously there's no LP sensor on these which sucks.

I'll report back when/if I figure out what the culprit is.

 

[KevinC39]

Well I don't really have an answer for you guys. I loaded a new map revision this week and the stumbling on cold starts went away. Which doesn't make sense because the previous revision I had been running since early November when I put the snow tires on and this problem didn't start until February-ish so who knows what's going on.

 

[mfractal]

Well I don't really have an answer for you guys. I loaded a new map revision this week and the stumbling on cold starts went away. Which doesn't make sense because the previous revision I had been running since early November when I put the snow tires on and this problem didn't start until February-ish so who knows what's going on.

problem might come back. I suspect it got better because once you flash your car with mhd,certain adaptations are reset. my thinking is that with time these adaptations will readjust to where the issue happens.

edit...
I took the liberty to upload your log to the datalog section and upon inspecting it I noticed that once your car goes closed loop (oxygen sensor heats up and is activated) your trims go 33% positive which is the maximum. Then ltft kicks in too to fix fueling. This is your issue. I bet that if you give it a bit of gas trims immediately drop. This is a clear indicator of a small vacuum leak or maybe a leak in your valve cover. Unmetered air enters pos maf which causes the trims to shoot up, once you give it gas and vacuum drops the trims normalize. Could you confirm my theory by logging a cold start just like you did and once you see stft goes up, give it a bit of gas and watch the trims go down.
that’s what causes your cold start problem too cause when the car is in open loop it gets a too lean of a mixture due to the air leak and dies.

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[KevinC39]

@mfractal hey thanks for the suggestion. Your theory makes sense to me. I'll get a log and see what it looks like. The valve cover gasket was replaced a few months ago but it's possible the cover had a crack in it that the shop didn't notice. I changed all the vacuum lines when I swapped the turbo but it's possible something has come loose or melted which might explain why everything was normal for the first several months with the new turbo and had no issues at all with the stock turbo.

 

[mfractal]

@mfractal hey thanks for the suggestion. Your theory makes sense to me. I'll get a log and see what it looks like. The valve cover gasket was replaced a few months ago but it's possible the cover had a crack in it that the shop didn't notice. I changed all the vacuum lines when I swapped the turbo but it's possible something has come loose or melted which might explain why everything was normal for the first several months with the new turbo and had no issues at all with the stock turbo.

easiest way to confirm my suspicion is with a log. if once you accelerate the trims drastically drop - there's a leak pos - maf for sure.

post the log once you make one. while logging cold start the car, wait for it to go closed loop (usually takes about a minute).
you can confirm it went closed loop once it starts showing LTFT and STFT numbers (btw you need to enable LTFT in the logging options, i think yours isn't enabled). Once it does, just accelerate lightly to say 3000 rpm, hold it there for a few seconds and then release. let the trims stablize again and post the log.

EDIT: i confused your logs with someone elses, your LTFT is on.

 

[KevinC39]

@mfractal took me a minute to figure out how to get the logs uploaded and posted but I think I got it. The first one I waited for the Stft to come up and then tried your 3k rpm cruise. The second is just a cold start from this morning and creeping out of the neighborhood.

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[KevinC39]

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[mfractal]

you can see it pretty well on the second log you posted. as soon as you hit the gas LTFT drops 15% and STFT also about the same amount.

If i had to guess it's what i said above. you have unmetered air sucked in post maf in high vaccum situations.

 

[KevinC39]

Thanks, I'll look around and see if I can find any loose or cracked hoses. It might explain why it's been a struggle getting this turbo dialed in. I'd really like to throw it on the Dynojet down the street and do a half mile event this year just to see what it does. Just gotta iron out these bugs.