Cylinder 7 Misfiring even after new plugs and coils

[atheris]

Good day everyone,

My car started misfiring giving the codes:

2B48: Combustion misfiring exhaust gas degassing Cyl. 7
2B3B: Misfiring with shutdown Cyl 7.

and on code starts the car makes a weird whining noise kind of sounds like a vacuum and gives a code after the vacuum noise disappears. The code listed below:

27BA: Fuel system LAMBDA / Fullungsplausi - Bank 1

and with another misfiring code

2B48: Combustion misfiring exhaust gas degassing Cyl. 7

Recently done the plugs and coils (also changed the PCV crankcase for the driver side because that was leaking), the car runs fine and no other issues when I clear code but this issue only happens on cold starts.

I just ordered a new air intake temperature sensor to see if that would fix the issue before emptying my wallet, just hoping to see if anyone has a similar issue that knows the fix. I've been reading the forums and still haven't found a conclusion

[Ajolives]

As a rule of thumb if something breaks right after I fix something (else)I go back and check the work.

If you haven’t already double check all connections and everything you touched, make sure the coil is pushed all the way down, spark plug tight, connections plugged in. If things seem well, I would try plugging in one of the replaced coils and see if the code goes away.

[spammysammich]

Only Genuine coils work on our cars. Aftermarket offerings currently in circulation cause misfires. Swap the old coil back in.

[atheris]

Everything was properly done, torqued the plugs to the correct spec, all connections are in, I even cleaned. Ill see if cylinder 7 is pushed down properly because I did have issues getting it back in (its in such a trash spot). I also did swap Cyl 1 and Cyl 7 and the misfire is still happening in the same spot which I found odd.

I'll keep updating on the solution if I find it.

[atheris]

Yes I'm aware, all coils are OEM straight from BMW (hefty penny) but I'll see if the misfire happens again with old coils.

[nick3753]

The misfire only started after you installed new plugs and coils? Or was there before and is still occurring after both were changed?

[atheris]

My bad, didn't give enough context, but it was misfiring before I changed the plugs and coils. Which is the reason why I changed them out, but still misfiring.

[spammysammich]

Either a misfire detection test in ISTA or a compression/leakdown test might give more info.

[atheris]

I'll see what I can do, will update.

[atheris]

So I started up the car, and it seems to only happen on cold starts. The car has a loud vacuum sound as it starts up, like a fan whining up, and after the fan stops the car instantly gives a code.

The codes are as follows:

2B48: Combustion misfiring exhaust gas degassing Cyl. 7
27C1: Info tank empty with error entry
279D: Power management battery closed circuit
27B2: Secondary air system throughput mainline.

I have a feeling the issue is sensor related. Let me know what you guys think.

[Ximian]

Originally Posted by atheris

Yes I'm aware, all coils are OEM straight from BMW (hefty penny) but I'll see if the misfire happens again with old coils.

Hello Bill Gates, didn't think you'd be on this forum. Did you keep your old ignition coils? Good idea to try one of those. Also double-check that the rubber boot from cylinder 7's ignition coil didn't stay behind somehow.

Originally Posted by atheris

So I started up the car, and it seems to only happen on cold starts. The car has a loud vacuum sound as it starts up, like a fan whining up, and after the fan stops the car instantly gives a code.

The codes are as follows:

2B48: Combustion misfiring exhaust gas degassing Cyl. 7
27C1: Info tank empty with error entry
279D: Power management battery closed circuit
27B2: Secondary air system throughput mainline.

I have a feeling the issue is sensor related. Let me know what you guys think.

Did you reconnect the secondary air pump hose after taking off the plenum and reattaching it? Or perhaps the hose was damaged. Diagram - https://www.bimmerworld.com/Exhaust/...727838504.html

[MidLifeM3]

Based on your description of symptoms, I actually doubt this suggestion is really your problem. But you may want to check anyway.

I found with my 2008 that when I sent my injectors out to be cleaned (at around 100k miles), the before and after test report showed that a couple of them were almost completely clogged, poor spray pattern, low flow, and leaking. If its bad enough, a clogged or malfunctioning injector could cause one cylinder misfire.

Pulling the injectors is a relatively easy job, and if you haven't had them cleaned before, the car is old enough that its probably a good idea to do it now and you can then rule out fuel delivery as a potential cause.