Happened to me twice before with my echo trimmer and I took it in both times. The guy told me that the exhaust was really dirty and needed to be cleaned out. If I were you I would try to clean the exhaust really well. If thats not it, take it in for a tuneup. It cost me about 40 bucks but they fixed that, plus gave it a tune up and it ran great. good luck
People who say it cannot be done should not interrupt those who are doing it.