[velimir]

Hello everyone,

Recently I bought a 2009 BMW 320i with the 4 cylinder N43 engine. The seller said that a check engine light appeared and went away 3 weeks before and suspected that it was due to a bad ignition coil, he said he replaced 2 a year ago and all spark plugs so it seemed very plausible.
For ~10 days the car ran perfectly, I drove it around 500km(~300 miles) then the check engine started blinking for a bit and then stayed on, but the car was still running fine so I decided to keep on driving to arrive home around 200km(~200 miles).

The next day the car was misfiring and shaking quite a lot on a cold start. After it wamed up it was fine.
The scanner showed a misfire on cylinder 3 and a running lean code. I inspected it and the spark plug on cylinder 3 was completely loose... and black all the way up the threads and a bit more, the ignition coil had some light brown looking dust on it.
I have replaced the spark plug and coil thinking they were damaged with new ones. NGK spark plug and Bosch coil.

The running lean code is no longer present, but the misfire still remains on cylinder 3, ONLY on cold starts. The car is no longer shaking, I can barely feel the misfires with my experience. Once it warms up it runs great.

I swpped the fuel injectors on cylinder 3 and 4. I coded them in as well, misfire still on cylinder 3.

I haven't reset any adaptations, but I'm not sure if that can be causing misfires?

Another thing I noticed is a disconected connector at the back of the intake manifold(see picture) I tried to touch around to see where it goes, but I coundn't find anything. Anyone knows what its used for?

View post on imgur.com

Any ideas what could be causing the misfire? What to look into next?

To elaborate on what happens on cold starts:
I start the car, RPM goes to 1100 after a few seconds it goes to ~750(all normal) then after 10 seconds it dips to under 700, then it jumps back up to ~1000 where it fluctuates a bit and the check engine light starts blinking.

[NZE90]

The N43 misfire detection software is notorious for being incorrect. It will report a misfire on cyl 3, when in fact it is a misfire in the previous cylinder in the firing order, in your case it will be number 1, as the firing order is 1-3-4-2.
Try swapping cyl 3 injector with cyl 1, then report back.

[velimir]

Originally Posted by NZE90

The N43 misfire detection software notorious for being incorrect. It will report a misfire on cyl 3, when in fact it is a misfire in the previous cylinder in the firing order, in your case it will be number 1, as the firing order is 1-3-4-2.
Try swapping cyl 3 injector with cyl 1, then report back.

I should swap the injectors per the physical order(1-2-3-4) right? I'm assuming I should wait till the next day to test if you're suspecting a leaking injector?
I also fixed the image not showing properly. Do you maybe know what that connector is for?

[NZE90]

Yes, take cylinder 3 injector and swap it with cylinder 1 and vice versa.

Not sure about the connector. Maybe the fuel tank vent valve.

[NZE90]

Seems highly likely it will be for the tank vent valve as the wire colours look the same (orange and white/grey)

Can you confirm the wires on your car are the same colours?

[velimir]

Originally Posted by NZE90

Seems highly likely it will be for the tank vent valve as the wire colours look the same (orange and white/grey)

Can you confirm the wires on your car are the same colours?

Yes I can confirm that it is the same colours. But its not for the tank vent valve, that is on the side of the intake manifold, and that one is connected properly as far as I know.

I guess it could be the same wires, that need to be connected somewhere else? I borrowed my mutimeter, so I cant test for continuity right now.

[NZE90]

According to ISTA, that valve in your photo is the "electric changeover valve, engine mount"

[NZE90]

Component B2231

[velimir]

Originally Posted by NZE90

According to ISTA, that valve in your photo is the "electric changeover valve, engine mount"

I see, alright, thank you for the help, I'll search around online for the tank vent valve location. And I will update you again once I've swapped out the injectors.

[velimir]

Originally Posted by NZE90

Yes, take cylinder 3 injector and swap it with cylinder 1 and vice versa.

Not sure about the connector. Maybe the fuel tank vent valve.

I swapped the two injectors about an hour ago, for now the misfire remained on cylinder 3, but I will test it again late tonight or tomorrow morning to let the injector have time leak into the cylinder.

In the meantime is it possible to check where the fuel tank vent valve is located in ISTA? I tried searching online but I couldn't find anything. Like the image you sent for the other component?

Also isn't the disconected conector supposed to throw another code?
All I get is:
1. 29CF -> misfire cylinder 3,
and maybe I should've meantioned it in the original post, but I believe its not connected,
2. A6CF -> Auc sensor.

[NZE90]

You may need to do a compression test on the engine if the misfire didn't change.

I think i may have discovered an error in ISTA as it is saying the tank vent valve and the electric changeover valve are the same thing. It's not unusual to have spare connectors in the engine bay so if there's no codes don't worry about it.

[velimir]

Originally Posted by NZE90

You may need to do a compression test on the engine if the misfire didn't change.

I think i may have discovered an error in ISTA as it is saying the tank vent valve and the electric changeover valve are the same thing. It's not unusual to have spare connectors in the engine bay so if there's no codes don't worry about it.

The misfire is still on cylinder 3.. unfortunately I do not own a compresson tester, so I'm tinking about taking it to a mechanic, since I do not have the space to fix it if it has a low compression in any of the cylinders. I would also need to buy a leak down tester + air compressor to see where the compression is being lost :/

I didn't know that spare connectors were a common thing. Good to know.

Thank you for all the help, and I will try to do an update once I know what's wrong with the engine.

[velimir]

Originally Posted by NZE90

The N43 misfire detection software is notorious for being incorrect. It will report a misfire on cyl 3, when in fact it is a misfire in the previous cylinder in the firing order, in your case it will be number 1, as the firing order is 1-3-4-2.
Try swapping cyl 3 injector with cyl 1, then report back.

I fixed it. It was so stupid ... You were right, the misfire detection software was messing up, but we messed up the cylinder order(physical / firing) :P Since the firing order is 1-3-4-2, I was supposed to check cylinder 2 (3 in firing order) which I had ignored so far partly becuase its hard to get the coil out from between the fuel lines to the HPFP.
Anyhow the spark plug on cylinder 2 also wasn't tightened properly from the previous owner ... which I just tightened and the misfire is now gone.

Thank you for the help, if I didn't know about the misfire detection software issues, I wouldn't have figured out what was wrong with it.

[velimir]

My misery returns.. I drove a couple of times, mostly city drives. One longer 40+40km(there and back) and the car felt like it was running a bit rough. No check engine light, I decided to scan for codes yesterday and it had these:

003104 - Rough running, stratified-charge mode
002c7f - Lambda control 2
002c6c - Mixture control to catalytic converter, system check

Today I cleared them and went to put some fuel in mainly to see if they would return and I got another misfire, no other codes from today:

0029d0 - Misfire cylinder 4

Additionaly the fuel consumption is currently ~7.5l/100km, the worst consumption was before I tightened(and replaced) all spark plugs, 7.9l/100km and before all these troubles it was at 6.9l/100km.

Can anyone suggest a diagnosing route?