act up

British  

verb

1. informal (intr, adverb) to behave in a troublesome way

   the engine began to act up when we were miles from anywhere

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act up Idioms  

1. Misbehave. For example, With an inexperienced rider, this horse always acts up . [c. 1900]

2. Malfunction, as in I'm not sure what's wrong with my car, but the transmission is acting up . In both usages up means “abnormally.”

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Example Sentences

He planned to keep the Prince Charming act up all night.

From Literature

The black flies are not the only troublesome creature acting up during the unseasonably warm weather.

From Los Angeles Times

I felt like all these isolated incidents were speaking to me to act up.

From BBC

Now, there may have been reasons why Buddy acted up.

From Literature

I listen for a whistle when she inhales, a sign her asthma is acting up, but don’t hear one.

From Literature