N54 surging feeling coasting or light throttle

LazySoo335i

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Jun 7, 2022
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Hey guys I'm chasing an issue I can't figure out.
2007 335i 6mt. Only mods are MHD and a dual cone intake.
Under coasting and light throttle I'm experiencing a surging or bucking kind of feeling. It disappears on deceleration or harder acceleration. I replaced the vanos solenoids but that didn't help. Car is healthy otherwise besides some wastegate rattle.
I'll attach a log I did with MHD. Not a pull as it doesn't seem to occur under heavy throttle. More light throttle and coasting instead.
Thanks in advance for any help
 

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  • timing corrections cruising and light throttle.csv
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SLOWESTN54

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I have the same issue, never been able to get to the bottom of it. I heard resetting adaptations with ista helps in some cases.
 

martymil

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its ignition related, could be a number of things.

Ecu mosfets on the way out if msd80
coil packs
shitty spark plugs, just because they are new doesnt mean good check resistance with a multimeter, plenty of guides on this
check harness ground wires or broken not so good connections, the engine loom could be shit.

So many things that can cause this and its a process of elimination
 

carabuser

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Oct 2, 2019
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Looking at your log it just seems to be the usual catalyst and O2 sensor diagnostic routines causing that surging.
You have the textbook helix pattern in your AFR readings:
1654635759755.png


Read through this thread (https://www.spoolstreet.com/threads/readiness-catalyst.7346/) , the fix is discussed along with table definitions so you can fix it yourself. You do need a custom map or a tuner that can apply the fix for you as the fix hasn't been added into MHD yet.

I did stumble across a neater way to disable diagnostic routines in the DME but haven't tested yet. The method mentioned in that thread gets the job done for now.
 

LazySoo335i

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Jun 7, 2022
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its ignition related, could be a number of things.

Ecu mosfets on the way out if msd80
coil packs
shitty spark plugs, just because they are new doesnt mean good check resistance with a multimeter, plenty of guides on this
check harness ground wires or broken not so good connections, the engine loom could be shit.

So many things that can cause this and its a process of elimination
So the coilpacks are Bosch and within 5000km, plugs are NGK and also within 5000km
I'll look into the other things you mentioned and report back
 

LazySoo335i

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Jun 7, 2022
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Looking at your log it just seems to be the usual catalyst and O2 sensor diagnostic routines causing that surging.
You have the textbook helix pattern in your AFR readings: View attachment 69492

Read through this thread (https://www.spoolstreet.com/threads/readiness-catalyst.7346/) , the fix is discussed along with table definitions so you can fix it yourself. You do need a custom map or a tuner that can apply the fix for you as the fix hasn't been added into MHD yet.

I did stumble across a neater way to disable diagnostic routines in the DME but haven't tested yet. The method mentioned in that thread gets the job done for now
Looking at your log it just seems to be the usual catalyst and O2 sensor diagnostic routines causing that surging.
You have the textbook helix pattern in your AFR readings: View attachment 69492

Read through this thread (https://www.spoolstreet.com/threads/readiness-catalyst.7346/) , the fix is discussed along with table definitions so you can fix it yourself. You do need a custom map or a tuner that can apply the fix for you as the fix hasn't been added into MHD yet.

I did stumble across a neater way to disable diagnostic routines in the DME but haven't tested yet. The method mentioned in that thread gets the job done for now.
Hey man so I read it and I'm still kind of confused, the tuning related stuff might be a bit out of my ballpark. But it possibly being the diagnostic routines, if it's happening with MHD installed and catted pipes checked on my stage 0 map, does that mean I could just replace the 02s to solve the issue? Or go catless and tune out that diagnostic routine?

I was on the verge of buying a new throttle body thinking it was that or the incorporated TPS, but you seem pretty certain seeing this helix pattern that it's related to this diagnostic routine
 

carabuser

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It's certainly caused by a diagnostic. Those lambda readings aren't a mistake, that's the DME applyimg lambda stimulation.

Doesn't normally happen on catted cars. Do you have any error codes?
 

LazySoo335i

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Jun 7, 2022
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It's certainly caused by a diagnostic. Those lambda readings aren't a mistake, that's the DME applyimg lambda stimulation.

Doesn't normally happen on catted cars. Do you have any error codes?
These are the codes im getting
DME active codes -
2A17 - DME: DMTL, system fault.
2D5A - DME: Monitoring engine torque limiting.
2F58 - DME: Automatic starting, activation.
2F6C - DME: Exhaust-gas flap, activation.
2FA3 - DME: No coding
 

carabuser

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These are the codes im getting
DME active codes -
2A17 - DME: DMTL, system fault.
2D5A - DME: Monitoring engine torque limiting.
2F58 - DME: Automatic starting, activation.
2F6C - DME: Exhaust-gas flap, activation.
2FA3 - DME: No coding
Looks like the car has a bad flash. Maybe a bodged backend flash with a region mismatch, that's quite common with JB4 cars.

You should first work on clearing those faults. A full flash with MHD should sort it. If you have a JB4 it's best to remove it and go flash only. Since you have cats fitted you should be able to flash an OTS map then after a short drive the readiness monitors will show complete.

With complete monitors the surging shouldn't occur.
 

LazySoo335i

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Jun 7, 2022
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Looks like the car has a bad flash. Maybe a bodged backend flash with a region mismatch, that's quite common with JB4 cars.

You should first work on clearing those faults. A full flash with MHD should sort it. If you have a JB4 it's best to remove it and go flash only. Since you have cats fitted you should be able to flash an OTS map then after a short drive the readiness monitors will show complete.

With complete monitors the surging shouldn't occur.
So I have the MHD stage 0 installed, but no jb4 no custom tunes either. I tried switching from my v10 stage0 map, back to stock, then to a v9 stage0 map to see if any difference and it was the same deal. I've cleared the faults multiple times, nothing changes and they all slowly reappear.

One other cause I thought, could my map sensor being going bad? I'm getting rediculously bad gas mileage right now too with my surging low end symptoms
 

carabuser

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So I have the MHD stage 0 installed, but no jb4 no custom tunes either. I tried switching from my v10 stage0 map, back to stock, then to a v9 stage0 map to see if any difference and it was the same deal. I've cleared the faults multiple times, nothing changes and they all slowly reappear.

One other cause I thought, could my map sensor being going bad? I'm getting rediculously bad gas mileage right now too with my surging low end symptoms

There's likely more than one thing going on with the car which is pretty normal with an N54. Bad mileage is typically injector related but bad O2 sensors can have a similar effect.

Start with getting the codes sorted then work through whatever problems remain after.

I believe MHD uses the UIF to work out the correct stock map for the car but if a previous owner has written a bad file then MHD will keep working with that ROM even when you use the stock map operations.

If you have access to WinKFP you can use comfort mode to update to the correct stock ROM. MHD will then work correctly in future flashes.

2FA3 should clear when you have the correct stock map applied and I expect the DTML fault to follow as that's usually triggered by a region mismatch. What region are you based in?
 
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Slowagon54

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So I have the MHD stage 0 installed, but no jb4 no custom tunes either. I tried switching from my v10 stage0 map, back to stock, then to a v9 stage0 map to see if any difference and it was the same deal. I've cleared the faults multiple times, nothing changes and they all slowly reappear.

One other cause I thought, could my map sensor being going bad? I'm getting rediculously bad gas mileage right now too with my surging low end symptoms
Sounds like the same i was fighting with on my B48. What Index are your Injectors and how old are they?
 

LazySoo335i

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Jun 7, 2022
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There's likely more than one thing going on with the car which is pretty normal with an N54. Bad mileage is typically injector related but bad O2 sensors can have a similar effect.

Start with getting the codes sorted then work through whatever problems remain after.

I believe MHD uses the UIF to work out the correct stock map for the car but if a previous owner has written a bad file then MHD will keep working with that ROM even when you use the stock map operations.

If you have access to WinKFP you can use comfort mode to update to the correct stock ROM. MHD will then work correctly in future flashes.

2FA3 should clear when you have the correct stock map applied and I expect the DTML fault to follow as that's usually triggered by a region mismatch. What region are you based in?
I'm in Canada , I was under the assumption the dtml code was for the charcoal canister, I've bought one just not installed yet as I didn't think it was contributing to my problem. The exhaust flap code I was told is from my exhaust being modded to keep the valve open.
Is winKFP an app I can download?
Also my injectors were checked a couple weeks ago and are all firing the way they should be, and wouldn't a bad o2 throw a code? Thanks a bunch for all the help carabuser
 

LazySoo335i

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Jun 7, 2022
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Sounds like the same i was fighting with on my B48. What Index are your Injectors and how old are they?
They are all original, index 1s, never skipped a beat so never changed them. I got them checked with a BMW scanner a few weeks ago and they are all operating the way they should be
 

Slowagon54

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Aug 21, 2020
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Huh... still on 1's. No matter how they have checked them, you should replace them. No way Index 1 injectors are still good after 15 Years imho.
 

carabuser

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Yeh you can't check injectors with a scanner. You need to visually inspect the spray pattern to get the whole picture. There are a few easier indicators first though:

Does your oil smell like fuel when you change it?
You can also check the plugs after pressurising the rail by cycling the ignition. If they are damp then that's a sign of a leak.

What does your readiness status show when you scan codes in MHD?
 

LazySoo335i

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Jun 7, 2022
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Yeh you can't check injectors with a scanner. You need to visually inspect the spray pattern to get the whole picture. There are a few easier indicators first though:

Does your oil smell like fuel when you change it?
You can also check the plugs after pressurising the rail by cycling the ignition. If they are damp then that's a sign of a leak.

What does your readiness status show when you scan codes in MHD?
It was some fancy BMW scanner at the euro shop near me. I think they could see how they were spraying at idle? I could be wrong, but they mentioned all were working even and the way they were supposed to. That was only at idle though, and I don't seem to have issues at idle.
I need an oil change so I will get it done in the next couple days and look for the gas smell.
The plugs are pretty well new but they are NGK and not colder step, but I'm also not modded so I figured they'd be good to go.
I will also post my readiness state from my scan with a picture
Screenshot_20220608-185307.png
 

LazySoo335i

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Jun 7, 2022
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Huh... still on 1's. No matter how they have checked them, you should replace them. No way Index 1 injectors are still good after 15 Years imho.
I'm going to go to my local shop and get them check spray pattern. See if they find anything odd. Since my problem only occurs during coasting or light throttle, should I have the car holding revs or under load while it gets checked?
 

carabuser

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Strange that readiness is passing but the diagnostic is still causing lambda stim.

Generate a stock bin from MHD and upload it here. I'll patch out the lambda stim and also check the region specific stuff like DMTL.