[n54flamer]

Recently have started having problems after installing/uninstalling catless downpipes in my 335 (n54).

After putting the stock cats back in, the car has very rough cold starts and misfires in cylinders 1,2 and 3. This happened with the catless downpipes as well. Once the car is warm there are no issues

Car has been walnut blasted, all plugs and coils have been changed, o2 sensors arent mixed up. Brand new turbos 25k miles ago.

Initially the vibrating originated from the downpipes rubbing against the subframe, however it is still evident with the stock downpipes in, with a bunch of clearance underneath.

Recently the car has been running sluggish, SES light is on with codes being:
2C31 - Lambda probe in front of catalytic converter, trimming control

any additional insight would be appreciated

[zmon1300]

any weird smoking issues? If you have already replaced plugs and coils, maybe look into injectors?

[n54flamer]

when the car was catless I would have heavy smoke following a cold start, but the smoke would go away after driving down a few blocks.

A week ago before I installed the catless downpipes, the car ran perfectly fine and healthy

[Spacecpe]

I bet money that your injectors are leaking .. let the cra sit overnight and take the plugs 1,2 and 3 out and see if they're wet or have a strong gas smell.

[limitdown]

You might have damaged one or both of your O2 sensors while installing your downpipes.
I had similar problems. I'm not sure whether my Indy damaged the sensors or if my sensors were alreadynon their way out.

[NoPwrOvrMe]

If you have a tune, disable it completely and see if it resolved anything. I had a similar issue it and turned out to be my tune.

[Jeff@TopGearSolutions]

Since it's cyl 1-3 misfire and front o2 sensor bank code it's almost with 100% certainty a failed o2 sensor.

It would be very uncommon to have all 3 injectors in 1 bank fail or be extremely weak enough at the same time.

[Mike@N54Tuning.com]

Originally Posted by limitdown

You might have damaged one or both of your O2 sensors while installing your downpipes.
I had similar problems. I'm not sure whether my Indy damaged the sensors or if my sensors were alreadynon their way out.

Thats what I was thinking..

Mike

[zmon1300]

check the plugs first, easier to check lol. let the car sit over night and then pull the plugs in the morning to see if they are wet or smell like gas. If not then 100% o2 sensor is bad. Good Luck!

[Tiago@VRSF]

Sounds like you swapped the o2 sensors. Black wires on the long pipe, gray on the short pipe.

[n54flamer]

pulled the plugs this morning and all seems well, all were dry and no obvious gas smell.

as of now I'm leaning towards replacing the o2 sensors, its likely that they were damaged when I initially installed catless downpipes, either that or they're just on their way out, I'm at 90k miles right now.

it seems as if the car is running worse and worse as the days go on, starting to feel awfully sluggish in normal driving, and when I go WOT. Still getting the same fault codes. Dropping it off at my mechanic on monday... ill keep you guys posted.

appreciate the help

[Cletus989]

My guess is injectors

[Chris@BoostConcepts]

At 90k, I would replace the O2's, they get slower with age, will run better with fresh ones in.

Also check your secondary cats to see if they are still in good shape.. Usually if you have a smoking issue either fuel or oil is in the exhaust and the secondary cats don't get as hot as the front and have trouble viewing off contaminates so they clog up. Good idea to inspect while you swap back to the new DP's.

[limitdown]

If it's an entire bank, then it's very unlikely to be injectors.

My issue was O2 sensors. I replaced them with Bosch's from ECS.
https://www.ecstuning.com/BMW-E93-33....0L/ES2580855/
https://www.ecstuning.com/BMW-E93-33....0L/ES2580856/

[n54flamer]

Just checked in with my mechanic - they're reluctant to change out the O2 sensors, claiming that its too labor intensive. They swapped out the coils and plugs - no luck. Swapped out all 6 injectors - still no luck. Right now theyre trying to find some electrical fault within the DME that could be triggering the bank 1 misfires. Im still suspicious that its one of the O2 sensors as this problem originated as soon as I swapped out the downpipes... however that wouldnt explain the misfires.

[JDuke335i]

Originally Posted by n54flamer

Just checked in with my mechanic - they're reluctant to change out the O2 sensors, claiming that its too labor intensive. They swapped out the coils and plugs - no luck. Swapped out all 6 injectors - still no luck. Right now theyre trying to find some electrical fault within the DME that could be triggering the bank 1 misfires. Im still suspicious that its one of the O2 sensors as this problem originated as soon as I swapped out the downpipes... however that wouldnt explain the misfires.

Since you're paying the bill , I would tell them to change the 02s , as that's most likely your problem since that's the last thing that was done b4 it started running like crap. Good luck !

[n54flamer]

Originally Posted by NoPwrOvrMe

If you have a tune, disable it completely and see if it resolved anything. I had a similar issue it and turned out to be my tune.

What tune were you running

[J. Dub]

Subbed to find out what the outcome is.

[n54flamer]

Update: Removed the intake manifold and there is a substantial amount of wet carbon buildup. I had the valves cleaned just under 10k miles ago, they were spotless after and its strange to see the amount of carbon thats present given the miles I put on the car after a carbon cleaning. The spark plugs are dry and black. The PCV system is obviously on its way out... prior to me purchasing the car a year ago the valves had not been carbon cleaned for 75k miles and I never experienced misfires or such a rough idle on cold starts, and they were just absolutely caked in carbon buildup.

Still strange that these symptoms would show right after I swapped the downpipes out and in. I did do a couple of hard pulls while the catless downpipes were in.

If the walunt blasting doesnt work, my repair shop will replace the plugs, coils and injectors. My car has been gone for 3 weeks now and Im starting to think that they're missing the problem completely at my expense...

[n54flamer]

here are the valves as they sit currently

[J. Dub]

what year is your e90? 10k miles and that much carbon? Makes me wonder what mine looks like after only 8k

[n54flamer]

its a 2009

the only engine modifications on it are a DCI, FMIC, M3 cowl and a tune, had AR downpipes but they have been removed

ive only put CA 91 octane in it throughout my ownership, previous owner babied it