Low RPM misfire ESS xpipe

[strokemycocktus]

I have a strange issue with my ESS xpipe - when I floor it around 2.5k rpm the car launches forward for a split second, then noticably slows down and picks up immediately after 3k rpm. Feels like the car is pulling timing. Not traction related, happens in every gear.
On stock xpipe it was all fine.
I had the catless ESS xpipe installed before and I can remember it was happening exactly this way, now I had cats welded in it, then installed and checked by a professional workshop which said there weren't any leaks.

Fresh gaskets installed.
Plugs are about 20k km old.
Car has 78k km now.
Throttle actuators rebuilt last year.
Second tank of 100 octane v power Racing fuel.

I thought that maybe it's just the custom xpipe with a stock tune thing, but I installed stage 2 tune from Alpine and it's still the same.

I'll post a video later.

Car has no fault codes. Where should I look for issues?

[Tut4u2]

You are running a stg 2 tune with cats in your xpipe? Could be related to that.

[strokemycocktus]

Originally Posted by Tut4u2

You are running a stg 2 tune with cats in your xpipe? Could be related to that.

I asked Alex about it twice and he said it's all right since they are high flow.
Besides as I mentioned I had exactly the same issue with a stock tune with or without cats, so I doubt it's tune related.

[SYT_Shadow]

I've run that xpipe for 40k miles, both catless and hfc, never experienced what you're describing

[strokemycocktus]

Originally Posted by SYT_Shadow

I've run that xpipe for 40k miles, both catless and hfc, never experienced what you're describing

Yeah I doubt this is strictly related to xpipe itself. Just saying it's occuring only with it on.

I tried flooring it in 6th at about 1500 rpm as I heard it could throw some codes then if the coils are bad, but nothing happened. The car accelerated better in this low range and fell on its face around 2.5k as usual. No codes or strange noises.

Should I run a very thorough inspection for exhaust leaks? Any other ideas?

[strokemycocktus]

That's a second gear pull. Not sure if it's audible here, I may record one more from 3rd maybe.

[SYT_Shadow]

Originally Posted by strokemycocktus

Yeah I doubt this is strictly related to xpipe itself. Just saying it's occuring only with it on.

I tried flooring it in 6th at about 1500 rpm as I heard it could throw some codes then if the coils are bad, but nothing happened. The car accelerated better in this low range and fell on its face around 2.5k as usual. No codes or strange noises.

Should I run a very thorough inspection for exhaust leaks? Any other ideas?

so you've tried a different xpipe (or oem) and the issue goes away?

besides the primary cats melting at the track and taking your engine out (...) the ESS xpipe has the forward X placement for max power so it's a great xpipe

[Godchild14]

Originally Posted by strokemycocktus

I have a strange issue with my ESS xpipe - when I floor it around 2.5k rpm the car launches forward for a split second, then noticably slows down and picks up immediately after 3k rpm. Feels like the car is pulling timing. Not traction related, happens in every gear.
On stock xpipe it was all fine.
I had the catless ESS xpipe installed before and I can remember it was happening exactly this way, now I had cats welded in it, then installed and checked by a professional workshop which said there weren't any leaks.

Fresh gaskets installed.
Plugs are about 20k km old.
Car has 78k km now.
Throttle actuators rebuilt last year.
Second tank of 100 octane v power Racing fuel.

I thought that maybe it's just the custom xpipe with a stock tune thing, but I installed stage 2 tune from Alpine and it's still the same.

I'll post a video later.

Car has no fault codes. Where should I look for issues?

Check your Sparks Plugs

[strokemycocktus]

Originally Posted by SYT_Shadow

so you've tried a different xpipe (or oem) and the issue goes away?

besides the primary cats melting at the track and taking your engine out (...) the ESS xpipe has the forward X placement for max power so it's a great xpipe

Yes, I swapped between the ESS and stock xpipe a few times and it was always present with the ess one and went away with the oem one.
I remember your thread, it sure didn't look good but on the other hand I do like 2-3 track days a year which is far less compared to what you did, so hopefully the cats will last longer. I am very happy with the x-pipe as far as sound and performance go, but this issue is very strange.

[SYT_Shadow]

Originally Posted by strokemycocktus

Yes, I swapped between the ESS and stock xpipe a few times and it was always present with the ess one and went away with the oem one.
I remember your thread, it sure didn't look good but on the other hand I do like 2-3 track days a year which is far less compared to what you did, so hopefully the cats will last longer. I am very happy with the x-pipe as far as sound and performance go, but this issue is very strange.

It is definitely strange... I've used the ESS Xpipe on 2 different M3s and never noticed something like this

[strokemycocktus]

I just read the codes again and it threw one this time - 27CE. It's for fuel pressure and is related to the fuel rail pressure sensor. Although I was running low on fuel yesterday so it may be because of that.

[strokemycocktus]

I noticed one more thing - I have cold start deleted now, and when I start the car in the morning I can still hear the ticking like with the cold start procedure on. So it does sound like an exhaust leak after all, right?
Would any leak at the header gaskets or headers themselves throw a code?

How difficult/expensive can the inspection or gasket replacement be?

[SYT_Shadow]

Originally Posted by strokemycocktus

I noticed one more thing - I have cold start deleted now, and when I start the car in the morning I can still hear the ticking like with the cold start procedure on. So it does sound like an exhaust leak after all, right?
Would any leak at the header gaskets or headers themselves throw a code?

How difficult/expensive can the inspection or gasket replacement be?

Unless you've changed headers it's very unlikely the leak is there

Most of the time the gasket in the engine-side connection to the xpipe gets turned around incorrectly or is just too worn to continue to provide a seal

[MaximusB]

SYT_Shadow
What caused your primary cats to clog/melt? I reading one of your post about it but forgot which thread it was in.

[strokemycocktus]

Originally Posted by SYT_Shadow

Unless you've changed headers it's very unlikely the leak is there

Most of the time the gasket in the engine-side connection to the xpipe gets turned around incorrectly or is just too worn to continue to provide a seal

I haven't touched the headers, but I can't speak for any of the previous owners. I know the car was supercharged at some point for a few thousand miles, so who knows.
The gaskets you mention were changed about 2 years ago and should be fine I guess. I am getting an exhaust inspection at a shop on Thursday, will let you know what they found.

I have also checked live lambda readings, all sensors were giving very similar readouts, all about 0.9-1.0 on idle and a bit above 1 when driving (also WOT at 2-3k rpm where the torque dip can be felt). Does it mean for sure the car isn't running rich?

As I mentioned I have an Alpine tune with cold start delete, but the car still starts with quite high rpm bump. I talked to Alex and he says something must be wrong with the car (he said it's most likely low battery but it's about 1 year old VARTA AGM and I have fully charged it with CTEK a few days ago, also the rpms drop a moment after a cold start). Here's a video of it starting in the morning:

Also I have more videos of the exhaust sound, if you could let me know whether that sounds like a leak or not I'd appreciate it. Car was fully warmed up, second video is with the camera just behind left front wheel.

[strokemycocktus]

Also, here are my adaptations for o2 sensors.

[SYT_Shadow]

Originally Posted by MaximusB

SYT_Shadow
What caused your primary cats to clog/melt? I reading one of your post about it but forgot which thread it was in.

It's described in these two threads in their opening posts. The second thread is the engine teardown

https://www.m3post.com/forums/showthread.php?t=1520978

https://www.m3post.com/forums/showthread.php?t=1698983

[strokemycocktus]

I've visited an exhaust shop today, they said they couldn't find any leaks and nothing is audible in their opinion. They didn't smoke test it though.

I have logged some data - I attach 2 low rpm pulls, one in 3rd an one in 6th.
RPM- red
AFR (Lambda) - green
Ignition advance - yellow

It's always the same - the AFR drops significantly always around 2500 rpm reaching 12.1-12.4, then jumps up to about 15 at 3200rpm and normalizes at 13.2-13.5 after that and stays like this until redline.

It doesn't look like I am having misfire, seems that the car is running rich at 2500rpm for some random reason.

I have also recorded a cold start - note that I have cold start deleted with my tune. Regardless, the RPM stays at about 1000 and the AFR jumps up to 30 about 20 seconds after startup, as if the cold start procedure was still on?

Again, I get zero fault codes. Car idles smoothly at 650rpm. The power delivery is strong and linear past ~3k rpm. High rpm performance seems to bo unaffected - I did a 9.9s 100-200 km/h pull with just the x-pipe on (stock tune).

Any ideas what to look for next?

[SYT_Shadow]

I was never able to get BMWLogger to work so I don't have any good info there.

We're just grasping at straws here, but have you tried logging with the stock tune vs the tune? see if the AFR at low rpm changes between them?

[strokemycocktus]

Originally Posted by SYT_Shadow

I was never able to get BMWLogger to work so I don't have any good info there.

We're just grasping at straws here, but have you tried logging with the stock tune vs the tune? see if the AFR at low rpm changes between them?

I'll check that today, thanks.
I've also read some posts with similar issues and decided to replace some parts in following order:
1. Low pressure fuel sensor
2. Pre-cat O2 sensors
3. Spark plugs (although they are only 25000 km old)

If anyone has some other ideas I'll definitely appreciate it.

[SYT_Shadow]

Originally Posted by strokemycocktus

I'll check that today, thanks.
I've also read some posts with similar issues and decided to replace some parts in following order:
1. Low pressure fuel sensor
2. Pre-cat O2 sensors
3. Spark plugs (although they are only 25000 km old)

If anyone has some other ideas I'll definitely appreciate it.

Some people have datalogged and after 16k km the car starts pulling timing vs new plugs.
I change mine every 10k miles (16k km)

On my stroker engine, after 6k miles the plugs were surprisingly bad so I'll be changing those out more often

[tdott]

Hmm, interesting, let us know what you find.

I had a similar hiccup when launching the car on alex's e85 tune, there would be a like pause around that rpm before power kicked in again, almost like you were letting off and getting back on it. (DSC off)

My plan was to get my injectors cleaned/flow tested once things return to normal.