Persistent N54 Misfire

[MBM6F]

So I've read just about every thread I could find on this... and couldn't really find a definitive answer.

Car is a 2009 135i with 65k miles, mods in sig. I drive it gently, probably too gently to be honest. I change the oil every 3-5k.

I started having a misfire on cylinder 6 a while ago, with no apparent rhyme or reason to when it was occurring. Since then I've done the following things:

Replace all plugs - (cylinder 6 was BLACK)
Swap coils - seemed to be fine
Swap injectors/reseal - Misfire remained in cylinder 6
Replace valve cover
Replace valve cover gasket
Compression check

The compression is good, the valve cover was cracked and the gasket wasn't great, so I was hoping that would fix it, but it did not do the trick.

Based on how I drive, I can see it being carbon buildup... I should probably get on it a bit more.

Anyone have any input? Any help would be greatly appreciated. I'm probably leaving something out here... but if I think of anything else I will add it.

[prcsa77]

Carbon cleaning may help. Most of my miles are on the highway so it took longer to develop issues (erratic idle at times, mild hesitation). Carbon cleaning made a world of difference on how the engine runs throughout RPM range and load. When I did my carbon cleaning of the intakes, #6 was the "wettest" of the intakes. Other than that, have you replaced the PCV? Have you had the oil analyzed, indicating possible fuel contamination? You said you swapped injectors, so the problem should have moved with it. t

[MBM6F]

Originally Posted by prcsa77

Carbon cleaning may help. Most of my miles are on the highway so it took longer to develop issues (erratic idle at times, mild hesitation). Carbon cleaning made a world of difference on how the engine runs throughout RPM range and load. When I did my carbon cleaning of the intakes, #6 was the "wettest" of the intakes. Other than that, have you replaced the PCV? Have you had the oil analyzed, indicating possible fuel contamination? You said you swapped injectors, so the problem should have moved with it. t

Thanks, many of my miles are from highway driving as well. I hadn't really thought of the PCV - I guess I assumed that would throw its own code or cause misfires on multiple cylinders.

I will see about having the oil analyzed tomorrow.

Thanks for the input. If anyone else has any tips or thoughts, please let me know.

[PA135i]

Just picked up my car today from a carbon cleaning. It had been about 45K since the last time I had it done. Much smoother acceleration... and idles better. had the plugs done too. Cylinder 6 was the worst also. Shop took pics, I guess they will give them to me Saturday when I go back for an alignment. I needed that because I replaced all 4 shocks with Bilstein Hd's

[MBM6F]

Originally Posted by PA135i

Just picked up my car today from a carbon cleaning. It had been about 45K since the last time I had it done. Much smoother acceleration... and idles better. had the plugs done too. Cylinder 6 was the worst also. Shop took pics, I guess they will give them to me Saturday when I go back for an alignment. I needed that because I replaced all 4 shocks with Bilstein Hd's

Thanks... at this point I'm really hoping it just needs a carbon cleaning. The car has never had one (just reached out to the previous owner today) which caught me off guard, for some reason I thought he had had one. Purchased the car last April with 51k.

[PA135i]

I drive about 13K miles a year. I have an N54 and it seems that every 45K is about right for a carbon cleaning. This fits in perfectly with when the plugs should be done and with the covers off the engine it's quick and easy.

[MBM6F]

So I'm pulling the trigger on the old walnut blasting... Hopefully that will get done tomorrow.

[heist_tub]

I had misfires on cylinder 3, 4, and 5 on and off for a while. replaced plugs and injectors and it still persisted. swapped coils around from the other cylinders and saw it wasn't that. So I had a walnut blast done finally and those were the ones that looked pretty bad (6 was BAD but didn't misfire lol). But anyways it's been about 2-ish weeks now and no codes have been thrown! I've driven soft and i've gotten on it pretty good. So if anything walnut blast might be your answer

[MBM6F]

Yep. My shop ordered a walnut blaster. Hopefully getting treated tomorrow.

[prcsa77]

Please post updates, good luck.
t

[Dackelone]

Originally Posted by MBM6F

Yep. My shop ordered a walnut blaster. Hopefully getting treated tomorrow.

Before you get it blasted... What kind of spark plugs did you use? Are you sure they are for your engine code? (n55 and n54 plugs are different!)

The reason I ask is... when I first researched changing my spark plugs on my n54... over on the e90forum I found a few posts where members were chasing a odd misfire only to solve the problem with BMW(dealer: OE) bought plugs instead of the aftermarket(OEM) Bosch plugs. The dealer plugs say BMW-Bosch, the Bosch plugs only say Bosch on them.

I would try a new set of plugs first.

Also... did you ever just try swapping spark plugs from that cylinder to another and see IF that changes anything? I only read where you swapped coils around.

[MBM6F]

Originally Posted by Dackelone

Before you get it blasted... What kind of spark plugs did you use? Are you sure they are for your engine code? (n55 and n54 plugs are different!)

The reason I ask is... when I first researched changing my spark plugs on my n54... over on the e90forum I found a few posts where members were chasing a odd misfire only to solve the problem with BMW(dealer: OE) bought plugs instead of the aftermarket(OEM) Bosch plugs. The dealer plugs say BMW-Bosch, the Bosch plugs only say Bosch on them.

I would try a new set of plugs first.

Also... did you ever just try swapping spark plugs from that cylinder to another and see IF that changes anything? I only read where you swapped coils around.

Thanks, that's good thinking. We did originally swap the plugs, but I will double check to see where the new ones are from. At this point, I think it needs a carbon cleaning regardless.

[MuNkY6913]

I had a misfire problem a couple years back that haunted me all summer. It even forced me to clean my valves myself with a brush. It started off with random misfires on wot. Very random. Not all the time. It progressively got worse but I was also getting an o2 sensor and all cylinder misfires. Different numbers and different banks would show up as misfires. Hell of a time finding what was wrong. After I ordered a new rear o2 sensor I thought I got shipped the wrong one. The connectors are different for the 2 rear o2 sensors. So if you unplug them it can only go back into the right one. Nothing stops you from putting them into the wrong downpipe. Haha. My car ran great or misfires all summer. Finally in the fall I figured it out. The video I watched for the dp install also showed the sensors in the wrong pipes according to the color of the wire. Both black sensors go in 1 pipe and both grey sensors go into the other. You can't run the car if you switch the front 2 sensors but it will still run with the 2 rears switched and give you misfires. Not sure if that is what's happening to you but it's easy enough to check.

[PA135i]

Are these the correct OEM BMW plugs to use: 12 12 0 037 244 part number
I told the Indy shop to use OEM plugs. Not sure if these are the ones.

[MBM6F]

Originally Posted by MuNkY6913

I had a misfire problem a couple years back that haunted me all summer. It even forced me to clean my valves myself with a brush. It started off with random misfires on wot. Very random. Not all the time. It progressively got worse but I was also getting an o2 sensor and all cylinder misfires. Different numbers and different banks would show up as misfires. Hell of a time finding what was wrong. After I ordered a new rear o2 sensor I thought I got shipped the wrong one. The connectors are different for the 2 rear o2 sensors. So if you unplug them it can only go back into the right one. Nothing stops you from putting them into the wrong downpipe. Haha. My car ran great or misfires all summer. Finally in the fall I figured it out. The video I watched for the dp install also showed the sensors in the wrong pipes according to the color of the wire. Both black sensors go in 1 pipe and both grey sensors go into the other. You can't run the car if you switch the front 2 sensors but it will still run with the 2 rears switched and give you misfires. Not sure if that is what's happening to you but it's easy enough to check.

I'll double check that, but I drove it for over a month with no issues or codes after having the DP's slapped on. I'll keep you guys posted.

Today went well because I was able to pick up an AW 135i bumper to throw on my car while my 1M rep is in the shop being repaired. Right now I'm spraying a set of washer covers for it. Really looking forward to getting my car all sorted out and finally being able to enjoy it again.

[MBM6F]

Finally have some time to update... Carbon cleaning took care of the misfire on cylinder 6, and man did it need it.

Now I occasionally have one on 2... This may take some time to sort out.

I'm going to triple check on what plugs they used.

[Pot_Pie_35i]

Originally Posted by MBM6F

Finally have some time to update... Carbon cleaning took care of the misfire on cylinder 6, and man did it need it.

Now I occasionally have one on 2... This may take some time to sort out.

I'm going to triple check on what plugs they used.

Were any of your misfire issues caused by an uncommon issue?