[nachob]

Originally Posted by ///BYU

I had something almost identical happen the other day. This is a good thread so I want to add to it instead of creating a new one.

I was cruising along between 2,000-3,000 rpm and decided to accelerate. I didn't floor it, but I did accelerate somewhat briskly. Just after depressing the accelerator, I felt power cut out twice in rapid succession. It almost felt like traction control was intervening when it shouldn't have been.

The same thing had happened a couple of days before under the same circumstances, so I decided to see if I could reproduce the problem again. I accelerated again (this time even more briskly - and without backing off right away like I had the previous two times). This time, I felt a definite shudder / stutter / stumble / loss of power AND the check engine light came on.

I wasn't expecting a check engine light and I wasn't really close to home. Right away, I went into the gentlest / smoothest cruise mode I could manage, while still going the speed limit. As long as I was cruising along, everything was normal, but I was getting a misfire with even less acceleration than before. I did what I could to avoid putting load on the engine. On iDrive, Vehicle Info >> Vehicle status >> Check Control showed "All systems OK," which I thought was interesting since I had a CEL. I had about 5 miles to go before I arrived at a meeting I was going to. Driving very gently, the check engine light went off on its own just before I arrived at my destination.

After my meeting, I had a 14-mile drive home. The car started up just fine, no check engine light, and I had an uneventful drive home. I definitely took it easy and, thankfully, didn't feel any misfiring.

I have Carly for BMW, so when I got home I connected it and ran the diagnostic. There was a fault - 0x29CF: Misfire, cylinder 3: injection is switched off. The freeze frame data show that the fault was recorded at 53,980 miles / 86,872 km, so I'm guessing the fault code is from the first time I noticed the problem, a few days before I actually got the check engine light. It also shows my engine speed at the time of the fault was 3,488 rpm and the engine temp was 93.75 C / 201 F. I think the "injection is switched off" note in the fault code indicates a preventative measure programmed into the engine software, not necessarily a problem with the fuel injection.



My (completely stock) 1M has 54,013 miles / 86,925 km and the spark plugs were changed at 28,160 miles / 45,319 km (25,853 miles / 41,606 km ago).

I think my options come down to the following:

Spark plug quantity: Planning to replace all 6 since I'm close to the replacement interval anyway

Spark plug brand: Planning on Bosch, but will think about NGK

Ignition coil quantity: Will do a little more research to decide if I want to just replace the coil for cylinder #3 or go ahead and replace them all. Leaning toward replacing them all, since I'm likely to go with Delphi or Eldor and I want all 6 coils to be the same brand (I'm guessing the original 2011 coils from the factory are made by Bosch)

Ignition coil brand: Bosch, Eldor, or Delphi. Leaning away from Bosch, will likely choose between Eldor and Delphi

Media blast / walnut blast: I was planning on doing this at around 60,000 miles / 100,000 km anyway. Rather than do it at the same time as replacing the plugs and coil(s), I'll probably wait a few weeks / months for two reasons. First, I'm curious to know if replacing the plugs and coil(s) solves the misfire problem - or if media blasting was really what I needed all along. Second, I want to know how much of a difference media blasting makes to how my car drives; I want to isolate this so any improvements can be clearly attributed to media blasting and not other changes that were made at the same time.

Fuel injectors: I'm only going to look at replacing injectors if new plugs, new coils, and media blasting don't solve the problem, which I'm pretty confident they will. Hoping I don't have to do anything with the fuel injectors because they're expensive little guys.

I'll update this post as I go.

Great post! Thank you. These are the ones that really make this forum valuable. They can help you troubleshoot based on these great descriptions.

As an owner doing the work, it makes sense to replace both plugs and coils. To me this does sound like a coil going bad more than plugs. It would make sense to replace all of them based on mileage.

As a tech person, and in the interest of "science" it would better to just replace the coils first to see how it idles and runs, then the plugs. That's of course just looking at it with my IT mind. Replacing the coils with the same Bosch plugs is probably the best real world test because I really don't think the plugs would cause this and it's close enough.

If you change the coils to Eldor or Delphi and also throw in NGK plugs all at the same time. You won't really be able to tell if something caused an improvement or if performance degraded, what caused it.

I would recommend replacing all the coils with the same BMW Bosch plugs to take away one variable and see how things run with your new coils.

I have done a few plug changes on E46 325i and 330i over the years. My best friend is also an independent Mercedes BMW mechanic. The E46 came with NGKs and I switched them to Bosch in the same heat range, etc. The idle was worse with the Bosch plugs. I thought maybe they weren't gapped as I was told they were. I sold that car and bought a 330i ZHP. It also came with NGKs and I got a set of Bosch plugs again thinking this time I will double check the gap. I did and they were gapped fine. I put them in and same thing. Idle not as good. Embarrased I reached out to my mechanic friend and told him what happened. He said, I wish I would've asked him first. He had run into the same issue on E46s going from NGK to Bosch and had even taken brand new ones out for a customer replaced them again with a warranty set of Bosch and no difference . Then he put the NGK plugs and it ran like perfectly. He has stopped changing between brands on BMWs now.

I personally have not heard of NGKs causing an issue, but I have seen Bosch plugs cause an issue in cars that came with NGK so I cannot say that Bosch has a problem. What I can deduce from this is that our cars are very complicated machines and changing spark plug brands CAN cause idle or other issues so for a good test of the coils, I would stay with the same brand, heat range and gap as the plugs in the car.

If anyone reading this has in fact changed their Bosch plugs to NGK without any other change. Let us know what your experience was.

Thank you.