[Sleeper340i]

Hi all,

Posted about this on the general F30 forum with good answers, but figured more input from people with the same car would be great too. I have a 2016 340i which I love, stage 2 MHD with ER high flow downpipe and agency power intake. Recently added the downpipe and intake a little over a month ago and the pops have been crazy since. I know I shouldn’t have but I ran max aggressive burble/pop settings on the high flow downpipe. The pops were nuts and I would do them all the time but problems arose a little after I started using the E30 MHD OTS Stage 2 map with the pops. The pops were more aggressive with the ethanol mix but one day the pops just stopped working and now it sounds like something just sputtering in place of the pops. The burbles are still there at low rpm but high rpm pops are completely gone.

I’ve tried reflashing stock map and messing with the burble settings but all to no avail. Around the same time I did get a catalytic converter error message which I coded off with MHD. Did I screw my O2 sensor or downpipe? I really miss my pops and I look forward to getting the AWE mid pipe or exhaust but wouldn’t be half as fun without the pops... and hypothetically speaking, if the cat is screwed could I just gut it and go catless, instead of purchasing a brand new catless or high flow downpipe? What are my options here guys. Any input is appreciated.

Also, the the car smells pretty bad if I’m right behind or in the garage with door open; and occasionally inside the car maybe once a day or every other day I smell rotten eggs. No problems at stops though.

[SC_B5X]

The rotten eggs smell is usually a symptom of bad cats, you could have messed up your cat, which I wouldn't be surprised with max burble settings.

I've never had this issue personally as I run a catless downpipe on my 340i as well as on my last car (335i N55).

[Mike@N54Tuning.com]

Originally Posted by SC_B5X

The rotten eggs smell is usually a symptom of bad cats, you could have messed up your cat, which I wouldn't be surprised with max burble settings.

I've never had this issue personally as I run a catless downpipe on my 340i as well as on my last car (335i N55).

+1

If you are smelling the exhaust it sounds as if the cats have been compromised.

Mike

[Sleeper340i]

Thanks for the input gents, if the messed up cat is the reason my
Pops fail that would be the best case scenario in my opinion. In this case, could I gut the cats in the downpipe and just go catless that way versus spending another 400 on another ER catless downpipe?

[bacon_45]

I'm pretty sure it's the O2 sensor. I have a catless DP and out of no where my super loud pops are gone. Sometimes they even sound muffled, so I believe it's a compromised O2 sensor!

[Sleeper340i]

Originally Posted by bacon_45

I'm pretty sure it's the O2 sensor. I have a catless DP and out of no where my super loud pops are gone. Sometimes they even sound muffled, so I believe it's a compromised O2 sensor!

You know what, this actually relates to another question that I had which makes me believe you’re right. On MHD lambda gauge my AFR is usually normal levels, but sometimes when I’m not on the throttle, it will go up to 236 or some crazy high level till I get back on the throttle, which would support that my O2 sensor is screwed if the two relate yes?

[SC_B5X]

Originally Posted by bacon_45

I'm pretty sure it's the O2 sensor. I have a catless DP and out of no where my super loud pops are gone. Sometimes they even sound muffled, so I believe it's a compromised O2 sensor!

How would an O2 sensor muffle your exhaust? They have nothing to do with the sound of the exhaust.

Originally Posted by Sleeper340i

You know what, this actually relates to another question that I had which makes me believe you’re right. On MHD lambda gauge my AFR is usually normal levels, but sometimes when I’m not on the throttle, it will go up to 236 or some crazy high level till I get back on the throttle, which would support that my O2 sensor is screwed if the two relate yes?

This is completely normal. When you are off the throttle your AFR's are going to shoot up because you aren't injecting fuel.