Im Englischen versteht man unter "putt-putt" ... oft ein kleines Auto,
I had never heard that used as a reference to a car, either. (I grew up with a true Putt-Putt golf course about a mile from my house, so that's what came to mind.) Urban Dictionary lists it in connection to cars, but many entries there seem to be simply some person's fantasy.
However, Merriam-Webster does include "putt-putt" in this sense as a variant of "put-put" (which I had never heard of either, so it appears to be used by at least some significant group of people.
variants: or putt-putt \ ˈpət¦pət , usually -¦pət+V \
Definition of put-put
(Entry 1 of 2)
1 : a sound made by or suggestive of the operation of a small gasoline engine
>the put-put of its motor
>occasionally there would be the rapid put-put of conversation
2 : a small gasoline engine or a vehicle or boat equipped with one
>a phonograph and a radio and a flivver and a put-put for the canoe
>experimenting with fast-flying combat planes to replace the slow-flying put-puts now used for the job
What's interesting is that if you look for "putt-putt" you see only the results for the golf courses with not link or reference to "put-put".