[N8N]

Good afternoon,

After trying to get my 335i in shape after years of not being driven much, I thought I had everything mostly squared away - yesterday I drove about 70 miles on the highway to pick up an old stereo receiver that I'd had serviced and everything was great. Went out to lunch today and on my way back the SES light lit up. It did feel a little rough and I pulled the codes (because I've been trying to get everything serviced, my Jeep was in the parking lot at work, and my scanner was in it... yeah, it's a good automotive month) and I've got a P0303 code.

I literally just replaced the spark plugs a couple hundred miles ago with new Bosch, so I am assuming that it is not those. My experience tells me that I should replace the #3 coil and/or move it to another cylinder to see if the misfire follows the coil. If it's the coil, great. If it's not, it's likely the injector, and I need to get ready to write a big, stinky check.

If I replace the coil, are there any that are better than the ones you get from the dealer?

Am I correct in assuming that this is likely either the coil or the injector? I know that the injectors were all replaced prior to my ownership (I bought it at 70K miles, it now has 151K) and one single one was replaced again, I don't remember which one or when.

thanks!

[N8N]

getbmwparts lists Delphi, Bosch, and Eldor for my car, all at the same price. Any idea which would be preferred?

[ky0u]

Originally Posted by N8N

Good afternoon,

After trying to get my 335i in shape after years of not being driven much, I thought I had everything mostly squared away - yesterday I drove about 70 miles on the highway to pick up an old stereo receiver that I'd had serviced and everything was great. Went out to lunch today and on my way back the SES light lit up. It did feel a little rough and I pulled the codes (because I've been trying to get everything serviced, my Jeep was in the parking lot at work, and my scanner was in it... yeah, it's a good automotive month) and I've got a P0303 code.

I literally just replaced the spark plugs a couple hundred miles ago with new Bosch, so I am assuming that it is not those. My experience tells me that I should replace the #3 coil and/or move it to another cylinder to see if the misfire follows the coil. If it's the coil, great. If it's not, it's likely the injector, and I need to get ready to write a big, stinky check.

If I replace the coil, are there any that are better than the ones you get from the dealer?

Am I correct in assuming that this is likely either the coil or the injector? I know that the injectors were all replaced prior to my ownership (I bought it at 70K miles, it now has 151K) and one single one was replaced again, I don't remember which one or when.

thanks!

Move the coil to test but also test the plug as well just in case. I know you mentioned just changing them but always good to be safe.

You can grab the Delphi or Eldor coils. The coils for the s55 m3 engines fit our cars if you want a more robust coil over the n54/5 orignals. I would advise you grab these (and any other parts you may need) from FCP Euro as it comes with lifetime warranty

Also, if the injectors weren't replaced at the dealer originally, I'd double check that they were calibrated in the DME properly. Idk if this can cause misfires but it can cause them to not operate 100% correctly

[N8N]

Unfortunately I chucked the old spark plugs

so Delphi and Eldor are preferred over Bosch?

Yes, injectors were all replaced at dealership. Whole set at Sterling, VA and one single at Tischer (I guess they're BMW of Silver Spring now)

Edit: good call on FCP Euro. Looks like I can get a set of 6 coils for about what 2.5 coils would cost at getbmwparts (Tischer)

[Phil325i]

This might help:

[ky0u]

Originally Posted by N8N

Unfortunately I chucked the old spark plugs

so Delphi and Eldor are preferred over Bosch?

Yes, injectors were all replaced at dealership. Whole set at Sterling, VA and one single at Tischer (I guess they're BMW of Silver Spring now)

Edit: good call on FCP Euro. Looks like I can get a set of 6 coils for about what 2.5 coils would cost at getbmwparts (Tischer)

You can test the plugs the same way you test the coils. Move the coil to another cylinder, then move the plug to a different one than the coil. Then see whic one the misfire follows (if it actually moves).

As for preferred, it seems yes, but also its a bit of a debated topic. Between they're actually better or if its just the difference between a worn set of coils and a fresh set.
But the S55 coils were used in a higher HP application than our OE Bosch and are running on quite a few e9x builds with at least double our stock power. And the price difference is negligible, so it's a safe approach if you're already saving them, if not simply to raise the max thresholds.

[N8N]

I'm not sure if I could induce another misfire, although I wasn't doing anything special, the only thing I can think is that it was over 80 degrees out so the engine probably heat soaked really badly making me think that it might have been a heat induced failure (although that could equally be a leaky injector I suppose)

In any case, do you have a part no./preferred vendor for these S55 coils? I am not averse to using a non stock part if it will be more reliable.

[ky0u]

Originally Posted by N8N

I'm not sure if I could induce another misfire, although I wasn't doing anything special, the only thing I can think is that it was over 80 degrees out so the engine probably heat soaked really badly making me think that it might have been a heat induced failure (although that could equally be a leaky injector I suppose)

In any case, do you have a part no./preferred vendor for these S55 coils? I am not averse to using a non stock part if it will be more reliable.

Delphi (s55 coils): https://www.fcpeuro.com/products/bmw...-12138616153-1

Eldor (newer OE): https://www.fcpeuro.com/products/bmw...or-12138657273

[N8N]

Oh, got it, so Bosch were original OE, Delphi are actually S55 but will work (I was confused because everyone was listing them for N54 as well) and Eldor are newer versions of the stock N54 coil?

[whyzee125]

Get a fresh set of Eldor's from FCP and never have to worry again! I'm about to do the same for mine.

[N8N]

I'm now home from work so I could watch the video, that helps, thanks

[ky0u]

Originally Posted by N8N

Oh, got it, so Bosch were original OE, Delphi are actually S55 but will work (I was confused because everyone was listing them for N54 as well) and Eldor are newer versions of the stock N54 coil?

Got it perfectly!

[N8N]

OK, I just ordered 6 Eldor coils... they were a little more expensive than the other two, but if they're the latest version hopefully they address the shortcomings of the others. My theory is it's cheaper than labor to troubleshoot, and I end up with new coils when a few of mine probably have 150K miles on them... hopefully this fixes it, if not, well I know what's next.

[N8N]

Cautiously optimistic. Amazingly the package showed up today so I left work at 4 and swapped all the coils (no plug moving, engine was hot) cleared the MIL and drove a couple miles including a couple WOT blasts and light never came back on, and I swear by the time I got back home the idle felt smoother. I did go with the Eldors even though the Delphis were cheaper just because I figured I might as well get the latest stuff. Hopefully this sorts it, if I'm reading the date codes on the old Bosch coils right, #3 was one of the remaining original ones so it's had 152K miles on it, guessing just the stress of R&R pushed it over the edge when I replaced the plugs or it was just its time. Thanks for the advice and hopefully I can have a clean dash for a while.

[N8N]

Hah. So today I took car on the highway for the 1st time since replacing the coils, I got no MIL but I *did* get an overheat when I got off to get lunch. Figger it's probably the water pump. Guess the car is going through its midlife crisis where it wants all the parts; I hope it gets over it soon. Guess HPFP is next...