mitsubisi engin miss
If you want some sort of answer, you will need to offer more information. There's are thousands of reasons for engines miss firing.
Also, the Suzuki Swift does not use a Mitsubishi Motors engine..just an FYI. Even if it did, more specific information is needed to address your question.
Search Suzuki Swift Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Suzuki Swift Experts