AFJSONRequestOperation with POST Method give "signature_invalid"

[aisgirish]

I am using OAuth1 to authorise API and get access token.
When I call POST method it give me "oauth_problem=signature_invalid".

 NSMutableURLRequest *request = [self.myClient requestWithMethod:@"POST" path:apiURL parameters:jsonObj];
    NSDictionary *dict = @{ @"Content-Type":@"application/json",@"Accept":@"*/*"};

    [request setAllHTTPHeaderFields:dict];
    [request setHTTPShouldHandleCookies:true];

 AFJSONRequestOperation *jsonOperation = [AFJSONRequestOperation JSONRequestOperationWithRequest:request success:^(NSURLRequest *request, NSHTTPURLResponse *response, id JSON) {
     NSLog(@"Success: %@", JSON);

     } failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error, id JSON) {
         NSLog(@"Header: %@",[request allHTTPHeaderFields]);
     NSLog(@"Error: %@", error);
     }];

     [jsonOperation start];

Please help me.