Datalog N54 Surging at light throttle

[aarons335i]

Hello, i am having an issue after letting off the throttle and easing back into the throttle the car will have a bucking feel to it. Seems to be more noticeable in sport mode.
2007 335i automatic
MHD stage 2
catless down pipes
DCI
Charge Pipe with TIAL style BOV
New plugs
New coils
anyone have any advice? i noticed the throttle position fluctuates a lot when it does it but so does all the other parameters. Any help would be greatly appreciated

datazap.me | aaron335i | V9

datazap.me

 

[carabuser]

Log afr on both banks, if they oscillate it's catalyst diagnostic related.

 

[aarons335i]

Log afr on both banks, if they oscillate it's catalyst diagnostic related

Here is the log both AFR's are on there, look at the throttle position, could this be a tps problem as the percentage fluctuates quite a bit

datazap.me | aaron335i | Data8

datazap.me

 

[carabuser]

Here is the log both AFR's are on there, look at the throttle position, could this be a tps problem as the percentage fluctuates quite a bit

datazap.me | aaron335i | Data8

datazap.me

That's not catalyst diagnostic related at least. The MAF request and MAF actual are oscillating though, I think that's the cause of the throttle movements. The throttle will move to meet the MAF target.

It's also strange that your WGDC is oscillating a lot, that's probably driving the MAF fluctuations. It's a bit of a chicken and egg scenario trying to work out what are symptoms and what could be causes but my feeling would be that the throttle is OK.

An easy first step would be to reset all adaptations and flash a different MHD map, maybe an older revision like V8 then see if there's any change.

 

[SLOWESTN54]

Interesting enough currently dealing with the same thing. I've checked everything, reset adaptations with mhd. What fixed it for me was resetting adaptations with Ista. Although, i may have noticed it again today, but it was -1 Celsius outside. Attached a Log i took before adaptation reset

 

[carabuser]

Interesting enough currently dealing with the same thing. I've checked everything, reset adaptations with mhd. What fixed it for me was resetting adaptations with Ista. Although, i may have noticed it again today, but it was -1 Celsius outside. Attached a Log i took before adaptation reset

The cause of your oscillations is very different. You can clearly see the big swings in AFR and fuel trims there. The feeling of your surging is being caused by the varying fuel mixture.

The catalyst efficiency diag routine will push the lambda values in opposite directions between the two banks. Yours are both headed in the same direction. Also when the cat efficiency diag runs it will keep the fuel trims steady so my feeling is that your issue comes from elsewhere.

That is on the MSD81 DME though, with you being on MSD80 it's possible the catalyst diag routine is very different and might operate on a different basis. Any strange behaviour that only happens during idle and cruise is often related to a DME diagnostic routine as they operate at times where the DME has spare processing capacity.

 

[SLOWESTN54]

The cause of your oscillations is very different. You can clearly see the big swings in AFR and fuel trims there. The feeling of your surging is being caused by the varying fuel mixture.

The catalyst efficiency diag routine will push the lambda values in opposite directions between the two banks. Yours are both headed in the same direction. Also when the cat efficiency diag runs it will keep the fuel trims steady so my feeling is that your issue comes from elsewhere.

That is on the MSD81 DME though, with you being on MSD80 it's possible the catalyst diag routine is very different and might operate on a different basis. Any strange behaviour that only happens during idle and cruise is often related to a DME diagnostic routine as they operate at times where the DME has spare processing capacity.

My understanding was afr and fuel trims are just following throttle position. OP wasn't logging AFR's or stft's id be curious to see if they are fluctuating similarly. His fluctuations seem worse then mine. Any input is appreciated. I had read a long thread on E90 post i believe were someone chased this issue for a long time, in the end it was caused by switching maps on MHD.

Edit: sorry i had only looked at his first log not the second.

 

[aarons335i]

BIG UPDATE! Switched to V7 Stage 2 map and problems are gone, uploaded new log and it looks completely different car feels a lot smoother. Check it out!

datazap.me | aaron335i | V7 flash

datazap.me

 

[rallen_85]

Could someone please help with this issues. I have a 2007 335i n54 FBO and I'm getting a surging if I let of the gas and slightly press it agian. I have tried resetting adaptations and I even switch back to the mhd stock and it still does it. Attach are the data logs, anybodt?

 

[Dyyd]

BIG UPDATE! Switched to V7 Stage 2 map and problems are gone, uploaded new log and it looks completely different car feels a lot smoother. Check it out!

datazap.me | aaron335i | V7 flash

datazap.me

Was this a permanent fix?

 

[digitalashley]

I may have to test this out too.

its strange I have it on my stage 2 plus car pretty stock. And also surge on my custom tuned 17t car also. Worse on the 17t car..

 

[SLOWESTN54]

Do you guys have the throttle oscillation fix checked in MHD. It’s fixed it for me back when I had a n54

 

[digitalashley]

Do you guys have the throttle oscillation fix checked in MHD. It’s fixed it for me back when I had a n54

I have tested that option it can work but for me it only seems to work for a period of time then doesn't make any difference. Stft are what oscillates on my car I can see on the MHD gauges.