[jpsanfor]

I have a 2008 335xi E90 MT with 146k Miles and pretty sure no performance modification have been made (black paint if that helps ) that has a persistent misfire. I will try to detail everything that I've done to the car but I am at a loss when it comes to finding the problem. I have done a lot of searching and I've tried several things but nothing seems to be helping my situation...

Complaint:
The car is misfiring and throwing the following codes at this time:

29E0 - Mixture Control
29E1 - Mixture Control 2
29CD - Combustion Misfire Cylinder 1
29CF - Combustion Misfire Cylinder 2
29CE - Combustion Misfire Cylinder 3
29CC - Combustion Misfire Several Cylinders
30FF - Charging Pressure Control, Boost Pressure Too Low
2D2E - Engine Electronics: Throttle - Valve Angle - Intake - Manifold Vacuum, Correlation

It seems like the car will usually go through the gears fine the first couple of times into a drive (manual g-box) and will sometimes cruise on the highway okay but eventually starts misfiring. If the car acts up it will sometimes misfire really bad and may shutdown the Bank 1 injectors in which case I can pull over and restart the car and it will clear up for a while. I have read fuel trims and Bank 1 has been very negative (-30) and also some negative on Bank 2 (-10 to -15).

Things I have tried:
1) I changed coils and plugs. The new components are Bosch. Bank 1 plugs were very dark/sooty, Bank 2 seemed okay. No carbon tracking that I noticed - no change in symptoms

2) I did a smoke test on the intake side and the rear diverter valve (Bank 2?) was faintly leaking at the connection to the charge pipe. Nothing else seemed to be leaking. The smoke test is however a lot less pressure than the boost pressure (also any idea what pressures I should be see on a stock application?)

3)I swapped the injectors bank-to-bank and recoded them myself - no change in symptoms

4) I swapped the upstream O2 sensors bank-to-bank (they're the same, just different length/color cables) - no change in symptoms

5) I have read about intake valve carbon build up and decided to pull the intake and found a lot of build-up so I used the CRC GDI cleaner as instructed (I sprayed it into both turbo intakes in the airbox:

https://www.amazon.com/CRC-05319-Int...ywords=crc+gdi

I figured if carbon build-up was my issue then the problem would have at least got a little better but - no change in symptoms

6) I tested the -08 injectors in a manner similar to this link:

I found that the injector that was in cylinder 3 originally and now in cylinder 6 was leaking. I was hoping this was the eureka moment, but I decided to replace the injectors with -12 (also re-coded) - no change in symptoms

7) I quickly swapped my new coils/plugs bank-to-bank after the injector change - no change in symptoms

Things I want to try:
A) Compression test. Its easy and cheap but I doubt that's my issue a little bit of milkiness on the oil cap is normal right?.

B) I know the 2007 models had DME mosfet issues but that was with the msd80. My car is April/08 which according to Realoem has the msd81 and I haven't read about any issues with those (I have not confirmed the part number on my actual DME) but I have seen ways to test the mosfets and It seems fairly straightforward.

C) Maybe the carbon build-up is still the issue and I need a walnut blast?

D) Both turbos seem to be pulling good vacuum when I have the airbox off and place my hand over each intake, still wondering about that Bank 2 diverter valve in the smoke test but it can't cause just a Bank 1 misfire right?

Hopefully I covered the relevant information and someone can point me in the right direction. Let me know if I can offer anything more to help out...

TL;DR I just have another n54 that developed a miss...

[RocketSurgeon]

What pressure did you use to boost test? You should be using 5-10psi, and you need to cap the pcv port on the rear turbo inlet. It should hold pressure VERY well. Mine would hold 8psi for at least a full minute. You have an underboost code, so you either aren't making boost, or it's leaking off. You could also check boost solenoids, vacuum lines, and wastegate actuators.

Liquids will not dissolve intake deposits, it requires mechanical removal like walnut blasting.

Be certain that your O2 sensors aren't crossed. Like you said, the connectors are the same.

Where did you get your index 12 injectors? Some people have been getting bad/counterfeit ones.

[jpsanfor]

Originally Posted by RocketSurgeon

What pressure did you use to boost test? You should be using 5-10psi, and you need to cap the pcv port on the rear turbo inlet. It should hold pressure VERY well. Mine would hold 8psi for at least a full minute. You have an underboost code, so you either aren't making boost, or it's leaking off. You could also check boost solenoids, vacuum lines, and wastegate actuators.

Liquids will not dissolve intake deposits, it requires mechanical removal like walnut blasting.

Be certain that your O2 sensors aren't crossed. Like you said, the connectors are the same.

Where did you get your index 12 injectors? Some people have been getting bad/counterfeit ones.

I'm not sure of the pressure when I smoke tested but I will try it again this weekend. It doesn't seem to me like the low boost would cause a misfire to me but idk?

Based on some testimonials it seemed like the liquid method at least should have helped. I figured I would at least notice an improvement but no difference. Planning on pulling the intake off this weekend and blasting. I got a kit from bav auto which I need a sand blasting pot anyway. It just doesn't seem like my symptoms indicate carbon build-up. No issues with rough idle at cold start. The car runs rough after warming up a bit and at cruising speed and later when up to temp under load, cruising, and idling. I can't wrap my head around the very negative fuel trims and terrible fuel mileage.

I double and triple checked the O2 sensors and even swapped just the connectors and it ran even worse so I think they're right.

I bought the -12's from FCPEuro

[hcopeland]

have you looking into the turbo? If 1, 2, and 3 are misfiring and boost is too low it sounds to me like a turbo. What exactly could be it but I think there are a few things you should check.

Carbon building in bank-1?
Turbo Condition?

I think the best thing to look into in the front turbo. It has to be either a problem with the turbo itself or a sensor.

Hope it helps!

[jpsanfor]

Originally Posted by hcopeland

have you looking into the turbo? If 1, 2, and 3 are misfiring and boost is too low it sounds to me like a turbo. What exactly could be it but I think there are a few things you should check.

Carbon building in bank-1?
Turbo Condition?

I think the best thing to look into in the front turbo. It has to be either a problem with the turbo itself or a sensor.

Hope it helps!

The idea Bank 1 turbo failure has certainly crossed my mind. I just don't have any idea how I would check it short of removing and examining it but it's a lot of work to do that. Especially with it being AWD.

The car seems to be pulling the same amount of air through each turbo. Not sure which sensors could be failed. I already tried swapping the upstream O2's. There doesn't seem to be any nasty smoke from the exhaust such as when a turbo is failing.

Update: Did some more reading on a thread here and I'm leaning towards clogged DP cat, I will investigate and update again.

[=C=]

Originally Posted by RocketSurgeon

What pressure did you use to boost test? You should be using 5-10psi, and you need to cap the pcv port on the rear turbo inlet. It should hold pressure VERY well. Mine would hold 8psi for at least a full minute. You have an underboost code, so you either aren't making boost, or it's leaking off. You could also check boost solenoids, vacuum lines, and wastegate actuators.

Liquids will not dissolve intake deposits, it requires mechanical removal like walnut blasting.

Be certain that your O2 sensors aren't crossed. Like you said, the connectors are the same.

Where did you get your index 12 injectors? Some people have been getting bad/counterfeit ones.

Looking at this video, this liquid ate up all the carbon build up without any mechanical work required.

OP, I suggest checking your MOSFETS. All my MOSFETS were OK, MSD80.

Me personally, I still have to replace my front O2 sensors. I have been putting it off as it's a PITA, however this video shows it rather simple job. While i'm down there I might as well change the DP's...

[Jklad]

It sounds like from the above you never actually verified what dme you have. Might want to do that first before you go dogging any further.

[RocketSurgeon]

There was another poster who confirmed a clogged precat issue with a compression tester. Apparently you can thread a compression tester into the precat oxygen sensor bung. His unaffected bank would not show any back pressure, while the affected bank showed 8 pounds of back pressure at 4000rpm. I thought that was a very clever way of diagnosing.
He was experiencing underboost, misfires, and weird fuel trims too. You could probably also visually inspect your downpipe if you prefer. A clogged cat will be all caked or melted.

[MysticRob]

Originally Posted by jpsanfor

5) I have read about intake valve carbon build up and decided to pull the intake and found a lot of build-up so I used the CRC GDI cleaner as instructed (I sprayed it into both turbo intakes in the airbox):

Say what now? If you pulled the intake and saw massive carbon build-up, why not just hit the intake valves directly instead of spraying the cleaner into the airbox?

[flashburn]

Man, I have done all the same work chasing the same Cyl 1 - 3 misfire.

Compression is 180 +/- 5 across all 6 cylinders.
New coils + plugs, twice in case I got a bad one.
New o2's
Moved injectors, problem stayed in Cyl 1-3
I just got the car back from a walnut blasting and it still runs the same.

Every time I pull a plug out Cyl 1-3 is very rich, 4-6 are all fine.

Then after this thread I've even pulled the DME, cracked it open, and tested the mofsets. I have a DME-80 but the injector mofsets all tested fine.

As a last resort, I also moved the knock sensors across each bank, the misfire stayed on cylinders 1-3.

Not to thread jack, but what else can I test/check? The theory above about a front turbo issue makes no sense to me because the boost is merged into a collector prior to going into the head. IE: If a front turbo were bad, it would not only affect cyl 1-3

[jpsanfor]

Update to all:

I did some work on the car over the weekend and found my problem and solved it... I was working under the plugged cat hypothesis and did some testing to confirm the issue. The first step was to determine if there was excess back pressure in the Bank 1 exhaust and I didn't have a way to adapt a pressure gauge to the O2 bung. I simply removed the Bank 1 O2 sensor and went for a quick test drive and the car drove great and pulled harder than when I first bought it so that told me the exhaust was blocked somewhere. I did some digging through the service records I received with the car and found the primary cats/down pipes had been replaced TWICE by previous owners which I think may have been caused by the leaking injector I found previously. I then put the O2 sensor back in and disconnected the exhaust just after the downpipes enough to cause a leak and test drove again and the car was great. That told me the secondary cat for Bank 1 was clogged so I "deactivated" it and drove it to work today. This thing drives better than when I bought it and pulls like a train now.

Originally Posted by =C=

Looking at this video, this liquid ate up all the carbon build up without any mechanical work required.

OP, I suggest checking your MOSFETS. All my MOSFETS were OK, MSD80.

Me personally, I still have to replace my front O2 sensors. I have been putting it off as it's a PITA, however this video shows it rather simple job. While i'm down there I might as well change the DP's...

I like the liquid cleaner but I'm sure a walnut blast is better and I plan on doing one in the next month. The liquid cleaner is probably good for managing the problem ever 10,000 miles as suggested. The O2 sensors really aren't that bad, I could probably do mine in about 30 minutes now. I'm not sure about the DP's on the RWD but I know since mine is AWD it will require lowering the subframe to remove them... or you can cut the rear cross member and reweld it like whoever changed the ones on my car previously. As I said before I'm pretty sure this car has the MSD81 (according to realOEM anyway) but I thought bad mosfets would make the car not run at all?

Originally Posted by Jklad

It sounds like from the above you never actually verified what dme you have. Might want to do that first before you go dogging any further.

See above

Originally Posted by RocketSurgeon

There was another poster who confirmed a clogged precat issue with a compression tester. Apparently you can thread a compression tester into the precat oxygen sensor bung. His unaffected bank would not show any back pressure, while the affected bank showed 8 pounds of back pressure at 4000rpm. I thought that was a very clever way of diagnosing.
He was experiencing underboost, misfires, and weird fuel trims too. You could probably also visually inspect your downpipe if you prefer. A clogged cat will be all caked or melted.

That's the thread that gave me the inspiration. Only difference being that my secondary cat was clogged.

Originally Posted by MysticRob

Say what now? If you pulled the intake and saw massive carbon build-up, why not just hit the intake valves directly instead of spraying the cleaner into the airbox?

I didn't have the cleaner when I had the intake off. Going through the airbox also gets the cleaner through the turbos.

Originally Posted by flashburn

Man, I have done all the same work chasing the same Cyl 1 - 3 misfire.

Compression is 180 +/- 5 across all 6 cylinders.
New coils + plugs, twice in case I got a bad one.
New o2's
Moved injectors, problem stayed in Cyl 1-3
I just got the car back from a walnut blasting and it still runs the same.

Every time I pull a plug out Cyl 1-3 is very rich, 4-6 are all fine.

Then after this thread I've even pulled the DME, cracked it open, and tested the mofsets. I have a DME-80 but the injector mofsets all tested fine.

As a last resort, I also moved the knock sensors across each bank, the misfire stayed on cylinders 1-3.

Not to thread jack, but what else can I test/check? The theory above about a front turbo issue makes no sense to me because the boost is merged into a collector prior to going into the head. IE: If a front turbo were bad, it would not only affect cyl 1-3

See what I did above. It's best to use an adapter and measure the back pressure through the O2 bung but simply removing the O2 sensor and going for a quick drive will tell you if that is the issue. I know mechanics will sometimes just drill a hole and weld it back up later. It doesn't take much of a hole to relieve the excess pressure.

Thanks to all for the help!

[flashburn]

Thanks for the update! Here's to hoping. I'll give it a try this week and report back as well.

FYI: Here is a video I took this weekend after my "chemical" clean. I had to take the manifold off to test the knock sensors. It worked a bit, these aren't as bad as they were, but they are far from the perfect the walnut blasting gives. It's certainly clean enough that it isn't the culprit of the misfire. This was done by an indy who bought some machine specifically for this purpose. They clean it without taking the manifold off. Knowing what I know now, I wouldn't do it again, and I'd just walnut blast it.

https://drive.google.com/file/d/1Uhk...ew?usp=sharing

[jpsanfor]

Originally Posted by flashburn

Thanks for the update! Here's to hoping. I'll give it a try this week and report back as well.

FYI: Here is a video I took this weekend after my "chemical" clean. I had to take the manifold off to test the knock sensors. It worked a bit, these aren't as bad as they were, but they are far from the perfect the walnut blasting gives. It's certainly clean enough that it isn't the culprit of the misfire. This was done by an indy who bought some machine specifically for this purpose. They clean it without taking the manifold off. Knowing what I know now, I wouldn't do it again, and I'd just walnut blast it.

That was after the chemical clean?! If so that doesn't seem like much of a difference. I bought a sandblasting kit from Bavarian Auto for less than $250 and that includes the blast pot which I want for other projects anyway so it was a decent buy. Not sure how they could do it without removing the intake. Personally, the intake isn't that hard to remove especially when I compare it to removing the intake on my E46...

The diagnosis of a plugged cat is pretty straightforward. I think people get hung up on the fact the error codes that they get are not indicative of a plugged cat since there is nothing in the programming as far as I am aware that would indicate too much back pressure and give you an error code.

[feuer]

Originally Posted by hcopeland

have you looking into the turbo? If 1, 2, and 3 are misfiring and boost is too low it sounds to me like a turbo. What exactly could be it but I think there are a few things you should check.
Carbon building in bank-1?
Turbo Condition?
I think the best thing to look into in the front turbo. It has to be either a problem with the turbo itself or a sensor.
Hope it helps!

.

[MysticRob]

Originally Posted by flashburn

...Here is a video I took this weekend after my "chemical" clean. It's certainly clean enough that it isn't the culprit of the misfire. This was done by an indy who bought some machine specifically for this purpose. They clean it without taking the manifold off. Knowing what I know now, I wouldn't do it again, and I'd just walnut blast it... I didn't have the cleaner when I had the intake off. Going through the airbox also gets the cleaner through the turbos.

https://drive.google.com/file/d/1Uhk...ew?usp=sharing

Gets the cleaner through the turbos? That still doesn't make sense. If that video is AFTER you need to start over and get it done right. Don't just look at the valves, look at the reduced intake runner area from built-up crud on the walls and valve stems too. Good to hear you found the issue though!

Originally Posted by feuer

That makes no sense bro.

LOLz, maybe oxygen deprivation from the LA fires.

[boulderlund]

I just added to my post here http://www.e90post.com/forums/showth...8#post22552688

As in your case, my problem was with the secondary cat. I had the cat replaced professionally for just over $400. Since your pre-cats were changed, it is likely that they disintegrated just like mine and sent debris back to the secondaries. The guy who did my repair said that this scenario is very common for cars with primary/secondary cats that come in for cat repair.

As a suggestion, it may be worthwhile to inspect the current pre-cats at some point to make sure that they have not been damaged also. I am not sure how long they last when they burn fuel from a leaky injector. I bought a lighted endoscope for $15 that works quite well. I think you could feed one in through the upstream O2 sensor port and have a look for very little money and effort.

[flashburn]

Originally Posted by jpsanfor

That was after the chemical clean?! If so that doesn't seem like much of a difference. I bought a sandblasting kit from Bavarian Auto for less than $250 and that includes the blast pot which I want for other projects anyway so it was a decent buy. Not sure how they could do it without removing the intake. Personally, the intake isn't that hard to remove especially when I compare it to removing the intake on my E46...

The diagnosis of a plugged cat is pretty straightforward. I think people get hung up on the fact the error codes that they get are not indicative of a plugged cat since there is nothing in the programming as far as I am aware that would indicate too much back pressure and give you an error code.

Yeah, I'm not super happy with the results and all they did was offer to run more cleaner through at cost... gee thanks.

I did a scope before the cleaning and these are definitely better, but for 400 bucks, not even close to happy...

Still chasing my misfire. After Christmas I hope to send a scope down the o2 bungs to see the state of my catalytic converters. My misfire came out of nowhere, no warning, no degradation, just BAM, misfire - so I'm skeptical it's anything to do with the cats. If the cat's check out fine, I guess I'll drop another 800 on injectors It's my last resort at this point, even though it's completely illogical! I've already moved bank 1 to bank 2 but it's still misfiring in cylinders 1-3.

[addictedtoboost]

Originally Posted by flashburn

Yeah, I'm not super happy with the results and all they did was offer to run more cleaner through at cost... gee thanks.

I did a scope before the cleaning and these are definitely better, but for 400 bucks, not even close to happy...

Still chasing my misfire. After Christmas I hope to send a scope down the o2 bungs to see the state of my catalytic converters. My misfire came out of nowhere, no warning, no degradation, just BAM, misfire - so I'm skeptical it's anything to do with the cats. If the cat's check out fine, I guess I'll drop another 800 on injectors It's my last resort at this point, even though it's completely illogical! I've already moved bank 1 to bank 2 but it's still misfiring in cylinders 1-3.

I wanted to give you an update, I just got my intake valves walnut blasted and wow it's total night/day difference! I no longer have any issues with misfiring WOT, car' has gained back lost hp/torque for sure. I can notice the difference. Even in DS mode it didn't misfire at all. If you haven't already try getting your intake valves walnut blasted.The throttle response is very nice as well.

[flashburn]

Well since I jacked the thread, I'll come back to it as well, and post my resolution.

I had a bad bank 1 catalytic converter. I did the same diagnosis as the OP. Pulled the misfiring bank1 O2 sensor, left it connected to the wiring harness but with the sensor removed from the exhaust. That allowed enough pressure by to allow the car to run fine. Everything in my conventional mechanics toolkit suggests this is NOT what the problem should have been. Even my 50yr veteran mechanic father thought it wouldn't solve it. However, that clogged cat was my problem. Good news, everyone sells their OEM cats when they get down pipes so they are cheap to replace!

I guess statistically it's interesting as well, that's a 2 for 2 among strangers?

Side note: the subframe drop on the XI to get the DP's out is not nearly as difficult as it sounds. Added about 20 minutes of effort, but worth every ounce of it! Those not willing to do this work - fear not!

DIY I used from bimmer space boost with nice pics

EDIT:Not sure why it won't link to it? Competition I suppose? Admin remove if not allowed.

Originally Posted by MysticRob

Gets the cleaner through the turbos? That still doesn't make sense.

What most don't realize is that walnut blasting isn't enough...for full performance benefits you have to use sand; it's the only way:
https://www.audiforums.com/forum/off...e-wrong-80267/

[MysticRob]

Originally Posted by FCobra94

What most don't realize is that walnut blasting isn't enough...for full performance benefits you have to use sand; it's the only way:
https://www.audiforums.com/forum/off...e-wrong-80267/

LOL, I read it and expected to see an April 1st date on that. I'll do the same, and expect great results for cleaning the throttle body, valves, and piston-tops. Sand also helps build strong bones so I mix it with my protein shakes to port and polish my throat and anus for better digestion.

@ flashburn, glad you found the problem too. Seeing this more and more lately, likely from the older drivetrains and higher mileage.

[muncie21]

OP (jpsanfor) have to commend you for your methodical approach you took to troubleshooting and resolving your issue.

Too many times people take the shotgun approach and start replacing parts with no understanding of how they are related to the underlying issue.