Quick answer
Before cleaning, engines often suffer reduced power, rough idle, or increased emissions. Afterward, many drivers notice smoother acceleration, quieter operation, and less smoke—though results vary by deposit severity.
Detailed answer
Prior to carbon cleaning, an engine may idle unevenly, struggle with acceleration, or emit more smoke. You could see fouled spark plugs or a sooty tailpipe, signalling that combustion is compromised. After a thorough carbon cleaning—be it via chemical soak, hydrogen treatment, or mechanical blasting—you’ll likely notice a reduction in engine noise, fewer jolts in heavy traffic, and improved pick-up on hills. Some owners even measure slight horsepower increases on a dyno. Of course, the degree of improvement depends on how heavily caked the carbon was and whether other mechanical issues linger. A well-maintained engine with minimal buildup won’t show dramatic before-and-after changes, but in cases of moderate to severe deposits, the transformation can be quite striking. Keeping a log of your car’s performance metrics (like fuel consumption or average speed) can help confirm the benefits. Ultimately, clearing away those carbon layers helps restore the engine to a more optimal operating condition, translating to a more satisfying drive.