Jerky Acceleration from Cold Start

Kaane

Private
Jan 7, 2019
31
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2008 535i
I am having jerky acceleration from cold start, it gets progressively better after a minute or so when it changes fueling modes.

When the car first starts it shows fuel mode 5... anyone know which mode that is? It then goes to 4, 10 and 2.

Here is a log that captures it.

I have new injectors , new turbos, new valve cover, new all vacuum hoses, no air leaks. I reset adaptations like 50 times. Even after it warms up it's not 100% smooth, it is way better but not perfect.

93 octane tune with 3.5bar sensor.

Any ideas?

https://datazap.me/u/kaane/surge?log=0&data=3-23
 

Kaane

Private
Jan 7, 2019
31
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2008 535i
Actually i forgot, I did replace the coils 3 months ago. All are new Bosch units. I don't have any misfires or anything else ignition related. Any other ideas?

Also what is weird is the log shows accel pedal position to be jerky too during cold start and smooths out once it warms up, I don't drive any different, should the accel pedal position be the same smoothness at all times? Does it do some weird filtering at cold start? Bad pedal?
 

Rob09msport

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Oct 28, 2017
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No you don't you can flash stage 0 not return to stock. Stage 0 is a stock tune for emissions and trouble shooting but still can use n20 or adv sensors bl coils etc
 

RSL

Lieutenant
Aug 11, 2017
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4, 5 and 10 are heating injection strategies and normal. OP is pretty much starting a cold motor and immediately driving off, shouldn't expect it to operate like it does under normal conditions. There are a lot of adjustments specific to post start/heating. It still wants to run -30° timing, fast idle, etc. and OP is driving through it for much of that log. Once it reaches mode 2, it's still far from "warmed up". It's still in cold tables, just no additional post-start/heating adjustments and should act more normal, as he is seeing. It doesn't hit the warm tables until ~162F ECT IIRC. If something is going on at full temp, there might be an issue. As far as the log above, seems a matter of impatience rather than something wrong with the car.

Should want at least some minimal warm up time before taking off on a dead cold motor. 1-2 minutes to at least get off the heating modes isn't a lot and far less than I wait on cold starts.
 
  • Agree
Reactions: Jeffman

Kaane

Private
Jan 7, 2019
31
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2008 535i
I get starting a cold motor and driving is not ideal, but sometimes idling for 2 minutes is just not practical. It still should not surge like that even when cold. I don't ever boost it when cold but I don't think driving at low loads is that harmful.

Even when fully warmed up the car still has a tiny bit of surge, not as bad as when it is cold, but far from smooth at low throttle.
 

RSL

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Aug 11, 2017
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If the main complaints are between cold start and initial mode 2, just know there are significant differences in play that effect operation.
 

CornFedBimmer

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Jul 19, 2018
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2007 335i sedan
Due to having a loud exhaust, I typically only let my car idle for 30 seconds to a minute or so in the morning after a cold start. I drive very gingerly however and typically don't exceed 2,500 RPM until the oil temp needle registers over 160 degrees. With that being said, my throttle response is roughly the same even when I'm pulling away with the motor cold. So the OP's car likely does have a legitimate issue if he's noticing increased jerkiness on cold starts
 

Rob09msport

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Oct 28, 2017
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I would agree especially if ambient isn't that cold. I wonder if connecting exhaust flap could help anything. I still say I would check gap on plugs and maybe upgrade ignition. But first is try a stage 0 map
 

RSL

Lieutenant
Aug 11, 2017
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For sure there could be an issue and Rob's suggestions all stand, just saying there are a load of additional temporary factors in play after cold start that will have a bearing on how it responds initially.

If there are issues at temp too, flashing to a stage 0 map with 3.5 MAP option checked, as suggested, would be a quick way to rule out anything specifically related to the tune that might be effecting it.
 

Rob09msport

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Oct 28, 2017
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Exactly I hundred percent agree with rsl but also sounds like this situation is compounded by hardware. Stock these cars are designed to be stupid resistant but the higher the state of tune the more the push the go pedal car goes simplicity goes out the window. That's why the stage 0 is a great tool. Right now nothing is in spec so if you flash a stock equivalent now you can expect oem performance.