n43 misfire

[jlandah]

I bought resently 2007 120i E87 LCI bmw. The engine runs ruffly when I start it cold and yellow engine foult light lights up. Also for the first 5 kilometers the ride is jumpy when I drive at steady speed. OBD reader gives foult code P0304 cylinder 4 misfire detected.

I removed and cleaned the VANOS solenoids and changed their places, but it didn't help at all.

Then I moved the ignition coil from the cylinder 4 to cylinder 3. Now OBD reder gave same foult codes for both cylinders. It seemed that at least one ignition coil is broken.

I bought four new orginal spark plugs and one new ignition coil. When I changed the parts, car ran smoothly for about two weeks with out any problems. Almost same problems started to occur, but not as bad as earlier. When I start the engine cold, it runs again ruffly and the yellow engine foult light lights up, but it goes away fast automaticly. When I drive the car it seems to work fine. So the problem occurs now when the car runs idle. OBD reader gives the same cylinder 4 misfire foult code and today also to cylinder 3.

Do you have idea what should I do next to fix the problem or narrow down the search?

[bmwdirtracer]

The ignition coil electrical plugs on BMWs of this era sometimes just don't want to make good contact. When you flip down the little lever to draw the plug onto the coil, make sure that you simultaneously squeeze the plug into the coil.

Furthermore, though: did you use an OEM coil , or a cheap Chinese thing from your local parts store? Did you use the factory-specified spark plugs?

[jlandah]

I bought OEM coil.

I have been using the car for a while now. Yellow engine foult light lights up and engine runs a bit ruff. OBD reader gives misfire codes for cylinders 3 and 4. New foult code has come up, P114B. Here is some information about that foult code:

Information saved in Fault code
Fault text
Fault description
Condition for fault identification
DME
277C - P114B
Oxygen sensor trim control diagnosis, bank 1
Post Catalyst Fuel Trim Via Oxygen Sensor System Too Lean (Bank 1)
Test condition:
RICH suspected under consideration of I-component (( 2 (K_LA_TRIM_DIAG_I_MAX_SCHW) recognition of I- component limit) leads to deliberate RICH/LEAN control activation;
If the pre-catalyst and post-catalyst oxygen sensors respond accordingly a trim control error is recognized.
Terminal condition: Engine running Voltage condition:
none
none
1) Check intake and exhaust systems for leaks; incl. HFM operation/ ..if no fault is present.. 2.) Conduct oxygen sensor test routine/ 3.) If the test does not produce any results and the trim control error is still present ->Replace the sensor before the catalytic converter
MIL on after engine runs 2x / no effects on drivability
Warning light: MIL
none
Condition for fault memory entry
Action in service
Fault effect and breakdown warning
Driver information
Service instruction

This engine has 3 Lambda sensors. Two(O2B1S1 and O2B2S1) before catalysators and one after(O2B1S2). Both sensors before catalysator gives about same values when the car is running. O2B1S2 gives value 0,4xx, it chagges a little but not that much.

Do you have any idea where the problem could be or how to troubleshoot the problem?

[bmwdirtracer]

Misfire codes and Lean Mixture codes are often directly related. Intake leaks and lean mixtures can easily cause misfires. However, your new code says that the sensor AFTER the cat is saying the mixture is too lean - which would tend to indicate that the pre-cat sensors are not seeing a problem. That could mean that the post cat sensor is bad, or one of the pre-cat sensors is bad....if it's a pre-cat sensor, it's probably the one for bank 2 (cylinders 3 and 4) because the misfires would likely contaminate it.

However, I'd highly recommend that you chase down the misfires, first and foremost....and deal with the mixture code, if it still persists after the misfires are gone.

Realoem isn't working right now, so I can't look up your car, and I'm not familiar with this engine. Is it a direct injection engine? If so, carbon clogging of the intake passages is quite possible. Meanwhile, though, have you unplugged both coils 3 and 4 and cleaned the plugs (both sides) with electrical contact cleaner, and very carefully made sure to push the plugs all the way on to the coils?

[Bassie]

Hello,

I have exactly the same issue with misfires on cyl 4. Car is a E87 120i 170bhp with the N43B20A engine. For weeks I'm trying to solve this problem. Car runs rough on idle, engine starts to shake. after 2 min EML comes on and than the engines realy start to run rough. Reading out Always says it,s misfire on cyl 4. With the AC on engine runs smouther but lost like because the RPM's are higher. What have I done so far(evrything with parts):

New coils
New spark plugs
Renewed all the sealings/gaskets/O-rings of the air intake
vacuumhoses
Both O2 sensors before cat.
Cleaned injectors
leak test in all 4 cylinders.

Any body has an idea what the issue might be?

Thanks in advance

[MichalKi]

Hello @Bassie,
Have you found the root cause of your issue?