[bmwkrakow]

folks,

suggestion requested, kindly help!

BMW E90 2008 , misfire on cylinder 2 during cold start. After misfire is fixed, approx after running 100kms, misfire will happen when starting the car on cold engine.
spark plugs replaced 2 times. First NGK and currently BMW spark plugs. Fuel pump replaced. Coils swapped between 1 & 2. Injector swapped between 1 & 2. Still misfire on cylinder 2.

Available options:
1. Test all 4 injectors and sometimes testing will do cleaning/fixing also as per mechanic since testing is done by passing high pressure fuel. cost of this will be $250
2. Replace all 4 injectors, this will cost $1250

What do you suggest? And what are other things i should ask mechanic to check and tell which will help me diagnose the problem?

[E93Dude]

Sorry to hear about your troubles. If its not any of the coils or injectors, then you may very well have an ECU problem, specifically your MOSFETs, which are 6 specific computer chips that control the voltage and triggering for each of the injectors.

Also, when you switched your injectors around for testing, did you reprogram your car's engine with the 6-digit codes that are printed on the side of the injector? If not, the ECU might not realized you swapped the injectors, and would be sending the wrong signal to those particular two injectors.

Here is a good video on MOSFETs, and what they do. If the MOSFET controlling cylinder 2 is fried, you can have that individual MOSFET replaced (requires removing old MOSFET, and soldering a replacement on the circuit board in the ECU). Otherwise, you will have to replace the whole ECU, and that can get expensive.

[bmwkrakow]

Originally Posted by E93Dude

Sorry to hear about your troubles. If its not any of the coils or injectors, then you may very well have an ECU problem, specifically your MOSFETs, which are 6 specific computer chips that control the voltage and triggering for each of the injectors.

Also, when you switched your injectors around for testing, did you reprogram your car's engine with the 6-digit codes that are printed on the side of the injector? If not, the ECU might not realized you swapped the injectors, and would be sending the wrong signal to those particular two injectors.

Here is a good video on MOSFETs, and what they do. If the MOSFET controlling cylinder 2 is fried, you can have that individual MOSFET replaced (requires removing old MOSFET, and soldering a replacement on the circuit board in the ECU). Otherwise, you will have to replace the whole ECU, and that can get expensive.

Thanks for the suggestion. I will check regarding the coding. But with mosfet if there is a issue, i will see problem with misfire all time or after running for few kms and that alao just while starting the car. Any thoughts on that?

[E93Dude]

I don't know enough about the different symptoms of a MOSFET failure to give you much more insight into whether or not it is truly responsible for the issues that you are having. Others on e90post know about this than I do.

But what I can tell you, is that given that you have swapped the coils and injectors, your problem may be with the ignition system (the ECU and maybe MOSFET). Have you checked your car's OBDII port for fault codes? You don't have to have a "check engine" light for there to be fault codes stored in the ECU. If you don't have bluetooth OBDII reader, and app for your phone - GET ONE. They are cheap and excellent diagnostic tools.

[bmwkrakow]

Originally Posted by E93Dude

I don't know enough about the different symptoms of a MOSFET failure to give you much more insight into whether or not it is truly responsible for the issues that you are having. Others on e90post know about this than I do.

But what I can tell you, is that given that you have swapped the coils and injectors, your problem may be with the ignition system (the ECU and maybe MOSFET). Have you checked your car's OBDII port for fault codes? You don't have to have a "check engine" light for there to be fault codes stored in the ECU. If you don't have bluetooth OBDII reader, and app for your phone - GET ONE. They are cheap and excellent diagnostic tools.

Below is the result from obd

Car Scanner ELM OBD2
DTC report
Selected brand: BMW

============1==============
P0302
Raw code: 0302
ECU: Engine control unit
Status: Pending
OBDII: Cylinder 2 - misfire detected
BMW: Cylinder 2 Misfire Detected

============2==============
30EA
Raw code: 30EA
ECU: Engine control unit
Status: Pending fault present, Validated and stored in non volatile memory, Validated fault present at time of request

============3==============
2AF9
Raw code: 2AF9
ECU: Engine control unit
Status: Pending fault present

============4==============
29CE
Raw code: 29CE
ECU: Engine control unit
Status: Pending fault present, Validated fault present at time of request, Validated fault has been present during this drive cycle

============5==============
30EA
Raw code: 30EA
ECU: Engine control unit
Status: Pending fault present, Validated and stored in non volatile memory, Validated fault present at time of request

============6==============
2AF9
Raw code: 2AF9
ECU: Engine control unit
Status: Pending fault present

============7==============
29CE
Raw code: 29CE
ECU: Engine control unit
Status: Pending fault present, Validated fault present at time of request, Validated fault has been present during this drive cycle

============8==============
30EA
Raw code: 30EA
ECU: Engine control unit #1
Status: Pending fault present, Validated and stored in non volatile memory, Validated fault present at time of request

============9==============
2AF9
Raw code: 2AF9
ECU: Engine control unit #1
Status: Pending fault present

============10==============
29CE
Raw code: 29CE
ECU: Engine control unit #1
Status: Pending fault present, Validated fault present at time of request, Validated fault has been present during this drive cycle

============11==============
C947
Raw code: C947
ECU: SRS/Airbag
Status: Pending fault present during this driving cycle, Validated and stored in non volatile memory, Validated fault present at time of request

============12==============
A670
Raw code: A670
ECU: Center roof module
Status: Test is inhibited by other DTC, Validated and stored in non volatile memory

[E93Dude]

That's.....a lot of fault codes.

I'd recommend you review this link on common BMW fault codes. I think you will find some useful information related to your problem.

https://bmwtuning.co/bmw-n54-common-fault-codes/

Since some of the fault codes may be tripped by others, I would recommend you clear all the codes, and continue to drive. As soon as you notice the misfire next time, rescan. Those initial fault codes registered will be your likely core cause of the problem.

One last point: I know you have changed your spark plugs at some point, but you may want to consider removing/reinstalling the plug on cylinder #2 and double checking that you have it inserted it securely and torqued it appropriately.

[e91Owner]

What engine is in your e90?

[bmwkrakow]

Originally Posted by e91Owner

What engine is in your e90?

2008 model, 1995cc, 170hp

[bmwkrakow]

Originally Posted by E93Dude

That's.....a lot of fault codes.

I'd recommend you review this link on common BMW fault codes. I think you will find some useful information related to your problem.

https://bmwtuning.co/bmw-n54-common-fault-codes/

Since some of the fault codes may be tripped by others, I would recommend you clear all the codes, and continue to drive. As soon as you notice the misfire next time, rescan. Those initial fault codes registered will be your likely core cause of the problem.

One last point: I know you have changed your spark plugs at some point, but you may want to consider removing/reinstalling the plug on cylinder #2 and double checking that you have it inserted it securely and torqued it appropriately.

After clearing the codes and running for 3kms, i see the following

Car Scanner ELM OBD2
DTC report
Selected brand: BMW
VIN: WBAPG31090VJ42003

============1==============
30EA
Raw code: 30EA
ECU: Engine control unit
Status: Pending fault present, Validated and stored in non volatile memory, Validated fault present at time of request

============2==============
30EA
Raw code: 30EA
ECU: Engine control unit
Status: Pending fault present, Validated and stored in non volatile memory, Validated fault present at time of request

============3==============
30EA
Raw code: 30EA
ECU: Engine control unit #1
Status: Pending fault present, Validated and stored in non volatile memory, Validated fault present at time of request

============4==============
C947
Raw code: C947
ECU: SRS/Airbag
Status: Pending fault present during this driving cycle, Validated and stored in non volatile memory, Validated fault present at time of request

============5==============
A670
Raw code: A670
ECU: Center roof module
Status: Test is inhibited by other DTC, Validated and stored in non volatile memory, Validated fault present at time of request

[bmwkrakow]

i have few questions:
1. i am using normal fuel and not premium fuel. does this make any difference when looking at misfire?
2. sometimes only when i start the car i see engine sign and if i will check with OBD adaptor i can see misfire in cylinder2. But if turn off the ignition and start again, there is no engine sign and no misfire information in OBD. Does this say that my engine is running on all 4 cylinders after the last misfire happened or my 1 cylinder is disconnected?

[E93Dude]

Originally Posted by bmwkrakow

i have few questions:
1. i am using normal fuel and not premium fuel. does this make any difference when looking at misfire?
2. sometimes only when i start the car i see engine sign and if i will check with OBD adaptor i can see misfire in cylinder2. But if turn off the ignition and start again, there is no engine sign and no misfire information in OBD. Does this say that my engine is running on all 4 cylinders after the last misfire happened or my 1 cylinder is disconnected?

Your profile says you have a 328...presumably with a 6 cylinder. Your post above confuses me a bit. Your car is not a 4 cylinder, correct?

The above aside, from the "refreshed" fault codes you posted, looks like 30EA is the interesting one: fault in Nitrogen Oxide (NOX) sensor, in the exhaust system. This measures the level of pollutants in your exhaust. It helps your car ECU decide how to vary the fuel/air mixture. Failed NOX sensors can cause your engine to stumble, although I can't say whether or not it would cause individual injectors to have trouble (as you originally noted). In the United States, petrol is low in sulfer, lower than in Europe. You mentioned that you have been running the low grade fuel...I would put half a tank of premium (low sulfer, if possible) fuel in your car, and pour in a bottle (or two!) of Cataclean (https://www.cataclean.com/). Drive your car hard and fast for 30 minutes. The Cataclean fuel additive may help burn off contaminants on your NO2 sensor, and stop the fault code. NOX sensors are expensive, so try this first!

Last thoughts, if you have INPA diagnostic software, there is a NOX sensor "refresh" procedure you can instruct the engine to run, but if you do not have a Windows PC and are already familiar with INPA, it can be a bit confusing to run. As I noted earlier, I would also double check that your #2 spark plug is properly screwed into the engine bore. If neither of these suggestions help alleviate your #2 misfire, then as I noted earlier, you may have a MOSFET failure in your ECU. Good Luck!

[e91Owner]

Originally Posted by bmwkrakow

2008 model, 1995cc, 170hp

You may also want to ask on the international forums. While most BMW engines are very similar, the majority of answers you will get here are from the N52/N54/N55 perspective. The N43 is unfamiliar to most people in the US which are the majority of people posting on this board.

[E93Dude]

Originally Posted by e91Owner

You may also want to ask on the international forums. While most BMW engines are very similar, the majority of answers you will get here are from the N52/N54/N55 perspective. The N43 is unfamiliar to most people in the US which are the majority of people posting on this board.

I read right over the OPs comment about his engine. Oops. I did not realize the euro 328s were sporting 4 cylinders back in '08. The basics of troubleshooting misfires should be largely the same, but I don't want to pretend to know the N43, N20, etc.

[bmwkrakow]

so i went for a inspection with BMW and these are the things they shared:
operation smoothness value is following:
cylinder 1: 108.90
cylinder 2: 128.70
cylinder 3: 360.70
cylinder 4: 118.60
* dont know the unit for above

compression ratio for each cylinders:
cylinder 1: 16.5
cylinder 2: 16.1
cylinder 3: 16.7
cylinder 4: 16.6

verdict: the defective injector cyl 3 must be replaced and not injector cyl2 that enters the fault in the fault memory of the DME1

short answer is: replace the injector and recommendation is replace all 4 injectors

whats your thought on this and what additional questions should i ask that will help me to isolate if it is really injector?
any experience with injector repairing as i see there are companies specialised in that and offer such services. Wanted to know how succesful are they in repairing? if success rate is above 80% then it is worth giving a try before replacing.

what are your thoughts??

[Stuiterbal]

What about carbon buildup? Did you check intake valves? Not sure if walnut blasting is a thing for these engines