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Drive Culture After a carbon cleaning, the car won’t run. Can anything be done?

My son had his diesel BMW carbon-cleaned the other day and now his car is now not working, whereas it was fine before. He didn’t even get it home. It started to lose power, and there was black dust coming out of the engine. There is a disclaimer on the back of the form saying they do not accept any liability for mechanical or electrical damage that may be caused. And he signed it! He is on a low wage. Any suggestions? – Jen

Frequently recommended to address poor running conditions, carbon cleaning as performed by most BMW dealers is done with crushed walnuts that are blasted into the engine cylinder to remove excessive carbon buildup.

The use of less-invasive walnuts dramatically reduces the chances of mishaps, but they can’t be completely avoided, hence the disclaimers.

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Occasionally, some owners do complain of the malfunction indicator light (MIL) appearing after this service, and simple issues can be addressed with an adaption or software update.

Considering that your son’s car was not driveable suggests to me that, at the very least, a fuel injector may have failed.

Without knowing the exact model and year, I can offer little in the way of an accurate suggestion, but newer common-rail diesels do tend to suffer from injector failure, with lack of fuel filter servicing being the root cause.

I hate to use the cliché “the straw that broke the camel’s back” but there was likely a pre-existing condition present and the carbon cleaning was just the catalyst for the ultimate failure.

Lou Trottier is owner-operator of All About Imports in Mississauga. Have a question about maintenance and repair? E-mail globedrive@globeandmail.com, placing “Lou’s Garage” in the subject line.

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