Need Need Help Troubleshooting High RPM Sputter

[540-S3]

I have all new sensors, new cats, fuel filter, etc. I have pressured tested the intake to 7lbs and repaired all leaks. Ongoing CEL at high RPM's with engine sputtering. Runs fine otherwise with no CEL unless I get on it.


Electric thermostat control final stage (This requires a new thermostat, but should not have anything to do with the problem)
Misfire detected, catalyst damaging, random or unknown cylinder
Misfire detected, catalyst damaging Cyl 8
Misfire detected, catalyst damaging Cyl 7
Misfire with low fuel (I have 25 miles left of fuel)

[mattmartindrift]

On your SC setup, high RPM = high load. Which leads to my first guess of spark plugs, spark-plug insulation boots, or coils.

Have you tested fuel pressure? How about under load? Have you made sure that the fuel pressure is rising at 1:1 ratio of the boost pressure?

MAFS?

Cam or crank sensors could also be a possiblity.

[540-S3]

On your SC setup, high RPM = high load. Which leads to my first guess of spark plugs, spark-plug insulation boots, or coils.

Have you tested fuel pressure? How about under load? Have you made sure that the fuel pressure is rising at 1:1 ratio of the boost pressure?

MAFS?

Cam or crank sensors could also be a possibility.

Since I get the same two misfires on 7 and 8, I am going to focus on the ignition as you suggested. Plugs are iridium that were replaced about 30k miles ago, so I will be looking at the coils and boots after I am sure the plugs are torqued.

The cam sensor is new and MAF was only a few points down when I ran the MAF test a few months ago. I also just cleaned the MAF.

[mattmartindrift]

have you thought about clogged/dirty injectors? It could cause #7 and #8 to spit a bit.

have you tried a bottle of injector cleaner? I believe the Techron Concentrate Plus is internet-rumored to work well.

[540-S3]

have you thought about clogged/dirty injectors? It could cause #7 and #8 to spit a bit.

have you tried a bottle of injector cleaner? I believe the Techron Concentrate Plus is internet-rumored to work well.

I use Techron and others on a regular basis.

Okay I swapped out coils 5 and 6 with 7 and 8. I filled up the tank and warmed up the car to 100 degrees Celsius. Ran 3 spirited runs with no hesitation. I will be driving 150 miles today and I will test again on my way home. I have a suspicion that the coils won't act up until they get heat soaked. I will keep you posted.

[540-S3]

Okay I am only getting a slight hesitation at high RPM after rolling the 2 coils. I have since ordered 4 new Bremi coils and boots. I am going to replace the 2 coils that gave me the misfires. Not sure what to do with the other 2 coils. Are the coils in cylinders 3 and 4 and 7 and 8 more susceptible to heat? Maybe I will just change out that bank and then do the other side later. Any input?

[mattmartindrift]

I would say not that they are more susceptible to heat damage, but maybe just luck of the draw?

how's your engine grounding and such? that can play a huge role in how readily a coil can fire the spark across the plug's electrode.


I say play around with the new coils and report back.

[540-S3]

Well I went ahead a replaced the whole bank 5-6-7-8. Then, because I am so anal about using a torque wrench, I stripped out one of the 2 holes that secures the plastic cover on the valve cover. Guess it is time to learn how to HeliCoil a new thread.

Anyway the car runs like it did when I first bought it. Very smooth linear power all the through the RPM range. This problem has been going on for a long time and if I never would have got the CEL and codes, I would still be troubleshooting this issue.

One interesting observation is that the 2 coils that were bad have a part number of 12131748017. The other 2 and the new coils are 12131748018. Is there are problem with the 17's? Why did they make 2 different coils?

I am looking forward to replacing the other side soon. If I find any 17's, I may swap them out now with 18's I removed.

[mattmartindrift]

alot of times they'll redesign a part and the new iteration will be released under a new part number. if you check www.realoem.com you'll often see comments like "(ENDED)" with a new/replacement part nearby.

[540-S3]

alot of times they'll redesign a part and the new iteration will be released under a new part number. if you check www.realoem.com you'll often see comments like "(ENDED)" with a new/replacement part nearby.

12131748018 is the only ignition coil for my car in RealOEM, but for the M5 the 12131748017 coil was replaced with the 12131748018. I was just trying to determine if the 17 had some inherent problem and should not be used. If you guys are having coil related symptom, I would check the part number on the top of your coils and see if you have any 12131748017.

I found this video and thought it was an awesome tool to find that elusive misfiring coil.

How to Diagnose and Replace an Ignition Coil or Coils on a BMW.