One huge gap in the story is, how did they get their Honda to the garage to have it checked out?
(the rimshot is just assumed here)
I think the perp needs more than a check up, sounds like she needs new plugs, points,and condenser, followed by a timing job.
I noticed that missing link in the chain as well.
On the one hand, they must have had it towed.
OTOH, there really was nothing stopping them from driving.