[2blackbimma]

What’s up everybody, I really did not want to make a new post for this but I have been searching for days and couldn’t find a post for this exact problem. Hopefully this can help others as well.

I have a 2008 328i n51 engine, I recently had car rough idling horribly making it inoperable and misfires in cyl 4,5,6. I swapped the coils around to see if misfire would follow. Codes now read cyl 3,5,6 misfires. Swapped coils back and misfires stil read in 3,5,6 not cyl 4 anymore… weird. Been about 28k miles since plugs and coils were done so I got whole new set by bosch.
I swapped the new coils and plugs yesterday torqued to spec, made sure coil was seated and sensor clipped in. Went to turn on the car after new plugs and coils got installed and it still rough idled not as bad as it was before but not a smooth idle whatsoever. Removed new plugs and coils. All of the New Plugs in each cylinder smell like gas now and ALL coils have white residue all on inside (running lean?).how is every cylinder affected now Sitting here trying to figure out wtf this can be because I am still only getting codes for misfires cyl 3,5,6 no other codes whatsoever. Using BimmerLink and a scan tool that reads a good amount of codes. Someone suggested the bank 2 upstream o2 because of my initial problem with the cyl 4,5,6 misfire and I was going to get it but now I have misfires in both banks. I also see people saying injectors because of the gas smell on plugs but wouldn’t I get codes for these things isn’t that why there’s sensors everywhere. Can it be the o2 sensor or injectors without throwing 0 codes for them?

Added photos of bank 1 and bank 2 upstream o2 connections to manifolds. Clean one is bank 1. The one with white residue all over it is bank 2.

[mainbearing]

If you are in Cali with a 08 N51, check to see that the 15-year 150K mile PZEV emissions has not expired first. The problems causing those codes should be fixed free. BMW will also replace that leaking valve cover gasket too. For free if still under the warranty.

[2blackbimma]

Yeah I’m past the warranty I got 178k miles but I got the valve cover replaced by Bmw Sd coils and plugs at 148k right before warranty was out and they honestly did a shit job cuz the cover or vcg is leaking and i had a cyl 6 misfire 3k miles after they supposedly swapped ALL the coils and plugs. Luckily that misfire was a simple plug and coil fix but now I’m stressing codes I get aren’t leading to any dam help

[mainbearing]

So the P030x codes now are all cleared?

The plastic valve cover is a big problem on these engines because they crack. If the dealer only replaced the gasket and not the cover, there is a good chance you might have to do that. There are plenty of threads on that matter.

I am not too familiar with BMW scan tools, but if you can pull mass air flow readings as well as fuel trims, and maybe oxygen sensor waveforms, that might tell you if the problems were with false air entry, leaky injectors or tired oxygen sensors.

With leaky injectors, typically you might have rough startup in the morning, but smooths out afterwards. And probably more misfires at low rpms than higher rpms, where the extra fuel gets used up.

[2blackbimma]

No the codes have not went away. And the dealership said they replaced the entire valve cover not just the gasket. Im going to replace the vcg but I don’t think that could be the cause for the issues I am currently having l. I have p0305 p0306 p0304 codes all bank 2 codes . I was trying to pull what I can with this diagnostic app. Here are some readings.
1.23v bank2 pre cat
1.78v bank 1 pre cat
0.41v bank2 post cat
0.41v bank1 post cat
97% bank1 pre cat
97% bank2 pre cat
12% bank 1 post cat
12% bank 2 post cat

[mainbearing]

I never knew how to diagnose these sensors, so other forum experts will have help you.

Anyway your bank2 upstream sensor voltage looks low. I'm not sure if some of the posts are relevant but the upstreams seemed to be around 2.0v. And downstreams would fluctuate around 0.15 - 7v.

Sinatra here unplugged bank2 upstream and his rough idle smoothed out. Also with another resetting the lambda adaptations.
https://www.e90post.com/forums/showthread.php?t=1743626

Say there are no vacuum leaks, which based on no bank 1 errors, that is probably the case. The oil on your cover then may just be from filling the oil. A thing you can test is to swap bank 1 with bank 2 (upstreams), and see if the codes move to bank 1.

For example codes become P0300, P0301, P0302 and P0303. The sensor lengths are different, so you will have to temporarily tie them over the valve cover without touching the hot exhausts. That is just my amateur's guess anyway. Swap when the engine is stone cold.

And make sure in the end the correct sensor is plugged into the correct connector.

Some INPA screen shots with Youtube video link:
https://www.e90post.com/forums/showthread.php?t=1492953

[2blackbimma]

Yeah I will see if I can find some post about how to do proper o2 readings. Thank you so much for the help anyways ! I am going to mark the upstream sensors and swap them to see if the codes go into bank 1. Will update in a few hours to see if I was able to get something ruled out

[2blackbimma]

So I just attempted to start the car after disconnecting bank 2 pre cat o2 . I didn’t get a lean smell from my exhaust and there wasn’t white smoke coming out this time but I am still getting rough idle and the same misfire codes but also p0050 for the o2 that I disconnected. Wasn’t getting the o2 code until I tried starting the car with it disconnected. Should I still try swapping the bank 1 and bank 2 up stream sensor to see if the misfires go into bank 1? Only ran the car for about 30 seconds because it sound like hell but the MAF reading was 1.47 lb/m. What should normal maf readings be at? I’m going crazy trying to figure out what the hell this can be

[mainbearing]

If the exhausts are warm or hot there will be more chance of the threads stripping. Of course it depends on how well the factory antiseize works.

Let it cool down for 3-4 hours and swap the sensors. Plug them in, and see if the codes move then.

As far as MAF, this member's 328xi has 10.9kg/hr. 1.47 lb/min is like 40.2kg/hr??

https://www.e90post.com/forums/showp...92&postcount=4

[2blackbimma]

Just got inpa downloaded onto my Mac so hopefully I can see better info on the car with that so I can narrow down what’s causing the car to run like this . Will post photos of what I see once I get this hooked up

[2blackbimma]

Haven’t gotten any closer to fixing the issue going to clean maf sensor today don’t want to just start throwing parts at it but here are the codes off inpa with some freeze frame data. I’ve also got rough running in all cylinder in inpa now. I am stumped probably gonna take in to an Indy shop in a few days to get a good diagnostic on wtf is going on with the car

[mainbearing]

Looks like you have cylinder #5 and #6 misfires (P0305 and P0306), and since they were multiple cylinders, you also got the third code P0300 (multi-cylinder misfires). These were the 3 of the 4 error codes INAP saw.

As far as the rough running, only cyl #5 is in the red zone. Does that mean the others in the green were actually ok? But 3-6 seemed to be the "rougher" ones.

Not sure what the calculated loads at 54-58% are. Looks like group 1 sensor is adding 25% more fuel and group 2 sensor is subtracting 14% less fuel.

It is interesting that your coolant temp was 34-36C (93-97F). I guess the engine had not yet warmed up?

[2blackbimma]

Yeah engine was not warmed up only had the car on for about a minute because of how horrible it idles. I assumed all cylinder were rough because I read somewhere on here that anything +- 0.5 is a rough cylinder and I also did check all my new plugs and they all smelled of fuel and all coils all had white powder on them. Is this an o2 sensor problem even though I am not receiving no o2 codes? Or did I do the worst I could have done and blow a cylinder ? Have not yet pressure tested will do tomorrow because I don’t know what else can cause this without anything other than misfire codes

[Bmw1939]

You say the valve cover is leaking? Is that not the culprit?

[2blackbimma]

I had the whole valve cover replaced by bmw dealership 29k miles ago I will get the vcg changed but I can’t see the valve cover leaking causing such a rough idle and misfire in cyl 5 and 6

[lui2143177]

Did you ever find the issue? Have a similar issue with an 09 328i N51.