Last week my car started misfiring. I scanned with INPA and got codes 274E Misfire detection sumcheck error and 2742 cylinder misfire on # 1.

1)My first thought was to check the plugs which were baked, replaced cleared codes but still misfired.

2)Then I moved to trouble shooting the coils, best way is to switch them to different cylinders and see if misfire moves with the coil. You can also idle the engine and unplug one coil at a time to hear for idle fluctuation. If nothing happens when you unplug the coil , the coil is defective. My coils check out ok but still bad misfire.

3)After researching on different forums I found was to check the injector. Fastest and easiest way is to get a long flat head screwdriver and place the tip at the base of the injector and listen at the end of it for clicks of it engaging and disengaging.

My #1 injector was faint while listening to it compared to the others ones.I removed the rail and cleaned 1&2 injectors with injector cleaner while pulsing with 12V. I put her back together cleared codes and started her up, running super smooth now .

So my advice here is the troubleshoot all parts before replacing them . I was thinking of replacing all of my coils thinking it would clear the misfire. Im glad I didn't , why waste my money on parts that are working fine. If anybody has any questions let me know. Im just so relieved it wasn't my intermediate levers like most people suggest.

Good Luck everyone

 

+1

Excellent example of methodical troubleshooting. Moving through potential causes, changing one variable at a time, is the way to determine the cause.

Of course you could have just taken the car to a stealer, who would have begun flinging parts at the problem until an answer was found (while you are in the parking lot shoveling money into a hole). Ha Ha.

Yeoman's work!

 

I am having the same issue with my 04 545i. Just bought it second hand from someone and got her home but figured since I don’t know how the vehicle was maintained, it would be a good idea to replace all spark plugs… after I put in the new OE plugs, she started idling ROUGH AND SPUTTERING… so my next step was to change the coil packs since I noticed that there was one among the 8 that was completely different in appearance from the other 7. Once the coil packs were swapped out the problem got worse! Now she actually will stall out on me. Replaced the caps with the rubber diaphragms on either side of the engine since I noticed when checking the oil after a long drive the previous day that one was completely missing (my husband had taken it off, and didn’t put it back on all the way, without me knowing about it) so I just replaced both of them, because why just do only one? That’s like replacing 1 spark plug….lol anyways now it’s even worse…. Throwing a P2189 and P2187 codes!! Any suggestions on what it might be???? I was debating replacing the upstream O2 sensors, but not sure if I should as of yet.

side note I also cleaned all 8 fuel injectors and tested them to see if they were all functioning properly and from what I could tell they were…. PLEASE HELP!!!!!!

 

Seems that you may be building in new failures with your attempts to fix the first issue.

It seems the car was running pretty good before you swapped the plugs. You shoulda stopped there and checked your work

Are the plugs you put in gappable? If so, did you check / set the gap on them (don't assume that they're right out of the box).

Where did you get the coils? Cheap no-name (or expensive counterfeit...) coils are a LOT worse than old BMW coils, and will very often cause new and exciting problems (lots of threads here attest to that).