Sharding- Primary shard very slow

I have a 1 config ,2 shards,1 mongos instance running on different machines.

When i am trying to query a particular field that has index.I am not getting the result that i was able to get in standalone environment.

And when i see the shard stats it says the primary shard takes more time and the secondary shard behaves as it is expected to behave without any issues.

Could any one tell me what might be the problem for this slow performance.

I am presenting the same problems, please that somebody says as you solve it

i got the same problems, how can i solve it.

Could you provide some more details about your setup? What's the query you're running and what's indexed? Can we see the .explain for the query? How do the results differ from the results in a standalone environment? Do you have unsharded collections in the same database that are being hit by queries? Why aren't you using 3 config servers? What version of MongoDB is this?