IT’s been driving me crazy – I’ve been trying to remember a book series that involved magic. I know that the general plot involved a woman driving up in a Rolls Royce and the protagonist starting the adventure through her and her car. I feel like maybe one of the books involved the magic causing hiccups that could not be uncured without a new magic spell.
Lost Classics of Teen Lit: Name That Book! 
This sounds like it could be the “Trick” series by Scott Corbett. Main character, Kerby, meets eccentric old Mrs. Greymalkin when he helps her get her shoe unstuck from a sidewalk grate at the park. As a thank you, she gives him her son’s old chemestry set. Througjt the series, Kerby is almost certain Mrs. G is a witch, while his more scientifically minded friend scoffs at the idea.
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