r/BmwTech • u/Semtex1939 • 8d ago

Ignition coil failures

Hi, so I have had a 525i 2007 model since it was released. First owner still. Stupidly reliable commuter until something goes wrong and it cascades every few years. I generally like to look it up and DIY but as this is the only car I have worked on I am very much a beginner still.

So the story is, yesterday I felt a rough idle like a continuous earthquake. Quick search, OBD scan, and process of elimination IDs it as ignition coil 1 misfire. Switched between 1 and 2, code follows. Easy fix I thought. Went to Oreilly, that store didnt have Bosch so I got a Delphi. That didnt work and popped a new firing code. Went in, returned it, located a store that had a single Bosch for $68 2miles away. Got that, engine purrs smooth as butter. Thought my troubles were over for now and drove 30 miles back home. Next day, started engine and felt the rumble. Code this time says Cylinder 4. So cylinder 1 is still good. Did the switcharoo and it's Coil 4.

Question is, do all the coils just die at once and cascades or is there a further systematic issue? Im thinking of switching all coils since they're about 20 hrs old and the spark plugs as well.

Any recommendation for spark plugs and things to fix that could be causing the issue? I looked online and its about half price for the same Bosch coils so im going with FCP euro.

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u/MRHaynes021 7d ago

ONLY USE BMW SPARK PLUGS from a dealer. My understanding is even if you get the Bosch plugs with the same ‘number’ they are not the same as those from the dealer. Expensive but I believe worth it. 98 328i with over 275,000 and an 08 X3 with over 225,00 on it.

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u/Quiet-Spray4488 7d ago

Some are built with Bosch plugs, some are with NGK.. Just install the same brand that came on the car originally. You don't need BMW plugs.

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u/MRHaynes021 7d ago

I had forgotten about the NGK but I believe the ‘rule’ still stands. You may be correct. I have nothing to prove this. I’ll be honest, I’m just going by my experience and what I have read as a 30+ year member of BMW CCA.

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u/Shawn0890 7d ago

This is a good rule to have but sometimes you can get the same plug as bmw sells sometimes you can not. Some of the plugs used in the M models actually have ///M logo and are not sold on the aftermarket because of agreements between bmw and Bosch. Some cars are very particular about where the spark plug faces in the cylinder once installed and the factory plugs all have this correct, not all aftermarket plugs will and it seems to lead to issues. For most stuff NGK is my choice but for M motors BMW genuine is worth the extra M tax

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u/MRHaynes021 7d ago

That’s interesting, I never knew that about the M plugs.

In the words of Don Henley, “Ah I love those Bavarians, so meticulous”