Utilizing full CPU cycle during mongoimport

Hi..

We have 4-shards with 1-Primary 2-Secondaries(1-Secondary Hidden). When there is mongoimport, mongo works smooth with good response time. But when we start mongoimport Mongo starts utilizing full CPU,  consumes 100% cpu cycles resulting very long response time. As per our observations it happens with 1 collections. This collections is used by 5 APIs. Please suggest how i can avoid this. Due to this my API giving me time-out error

Thanks in advance