Case Studies

BMW Service – Ignition Coils – Catalytic Convertor Replacement

BMW Service – That flashing red or yellow Check Engine light? It means something, and on later model BMW, Audi, Mercedes, and other imports, it frequently means that one or more ignition coils have given up the ghost, especially if you’ve got 80,000 to 100,000 miles on the odometer.

Bosch coil, Bosch is OEM for BMW on this part.
Bosch coil, Bosch is OEM for BMW on this part.

So what is the ignition coil? Quite simply, this small little electronic device provides the voltage that fires the spark plugs, and is the heart of your BMW’s engine performance…unfortunately, it’s also one of the key things that can disable or damage the car. In this case study, the car came out of the BMW dealer, and had been previously serviced by another shop, who had installed incorrect, aftermarket coils. It was towed to our facility for diagnosis and evaluation. Unfortunately the defective ignition coils damaged the catalytic convertors on this nice BMW X5, leading to an expensive replacement of both convertors. My Mom, a retired nurse, taught me well, “An ounce of prevention is worth a pound of cure”, and nowhere is that more true than here with the ignition coils. Read on to see how the Atlantic Motorcar Center handles this problem.

Ignition coils are key to the efficiency and performance of your BMW and newer cars have 4, 6, or 12, depending on the engine size. They’re just as important as spark plugs. Starting with the M42 engine in 1990, BMW’s ignition systems use an individual coil for each cylinder (coil-on-plug ignition). This system, while offering better performance than the old single coil system, does have a shorter lifespan. We see coil failures between 80 and 100K miles, and have developed a service procedure, outlined below, do this right the first time.

As we mentioned, this car came out of the BMW dealer, and had been previously serviced by another shop, who had installed incorrect, aftermarket coils. The engine was not running correctly, and unfortunately the car was driven for some distance. With a faulty coil, the spark plug is not igniting the air/fuel mixture properly and that can lead to problems anywhere in the engine and exhaust (including catalytic converters and O2 sensors). In this case, it damaged the convertors, melting the ceramic monolith structure inside.

Correction and Prevention
BMW recommends replacement of the spark plugs on it’s newer cars at 90-100K miles. We agree, and also suggest replacement of all the ignition coils at the same time, to prevent problems just like this. In the past we’ve seen cars come in one new coil, then a short time later we see the same vehicle again for yet another coil, reminds me of the old christmas tree lights, one fails, then another, then another. Since all the coils have the same miles on them, it just makes sense to replace them at the same time.

In this case, we replaced the ignition coils with the correct type, also replaced the spark plugs. The vehicle was then road tested, and when the convertor fault returned, we verified and replaced both catalytic convertors, then carried out another extensive road test, just to be certain, before returning the car to the customer.

We advise our new customers all the time to make certain that their car ends up with someone who really knows, and cares about it. This is just another example of “knowing” rather than just “woking on” on BMWs, the whole ounce of prevention thing. It’s not the fancy building (think about who pays for that), but the people inside who fix the cars…

So how do you find an ethical shop, judge by the reviews online, by meeting the service team, by asking friends. Then once you have a quality facility, support them, build a relationship with them. You wouldn’t “shop around” every time you need a dentist for dental work, so go to the folks who know and respect you, and your car. If you are out of our service area (we cover Falmouth, Freeport to Camden), call and ask for a referral to one of our service network members. Your car, and your pocketbook will thank you. And so will the AMC Team.

Questions, or if we can be of help in any way with service on your BMW, or other European (and now Japanese) import, please contact us. Our team of Service Specialists are here to help, for even the newest autos! (207) 882-9969.

Knowing, not just “doing”, that’s the Atlantic Motorcar Center way of life.

The Atlantic Motorcar Center Service Team

Feel free to call or stop by find out more on how we can help you get your car back to the condition you both deserve! Earning your trust, every time you turn the car…that’s what we do…every day…for the last 30 years.

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If you have questions, or if we can be of further assistance, just call us at (207) 882-969, we’d love to meet you, and your car!

Bruce and the AMC Service Team

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