Prosody is the stress, intonation and rhythm of language.
People with ASD tend to have to poor control in prosody, in both reception (listening) and production (speaking). And because each language has very different prosodic features, the rhythm of a second language in an EL with ASD might never be mastered.
With respect to lexical stress, there is a decreased accuracy on a range of prosodic functions for persons with ASD, for example, forming a question versus comment, emphasizing, or indicating an emotional state (Peppé and McCann, 2003).
Persons with ASD tend to produce an exaggerated pause in a multisyllabic word, especially when the stress is on the second syllable. The length of utterance on the stressed syllable can be notably longer than typically developing peers (Grossman, Bemis, Plesa Skwerer, and Tager-Flusberg, 2010).
Grossman, R. B., Bemis, R. H., Plesa Skwerer, D. Tager-Flusberg, H. (2010, June). Lexical and affective prosody in children with high-functioning autism. Journal of Speech, Language, and Hearing Research, 53, 778-793.
Peppé, S., & McCann, J. (2003). Assessing intonation and prosody in children with atypical language development: The PEPS-C test and the revised version. Clinical Linguistics & Phonetics, (17), 345-354.