hightraffic php site problems

[Juergen Gotteswinter]

Hi,

i got some problems with a high loaded php site running nginx + php 
(without fpm).

i get the following error message from time to time:

162503979 upstream timed out (110: Connection timed out) while reading 
response header from upstream,


While this occours, nginx stops delivering php content and drops the 
error document.

Heres a part of my nginx conf

user    webuser1 nginx;
worker_processes        4;
worker_rlimit_nofile    65000;



#error_log             /var/log/nginx/error.log debug;
error_log               /var/log/nginx/error.log  notice;
#error_log             /var/log/nginx/error.log  info;

pid                     /var/run/nginx.pid;



events {
     worker_connections  8192;
     use epoll;
}



http {
     include             /etc/nginx/mime.types;
     default_type        application/octet-stream;

     log_format main      '$remote_addr $remote_user [$time_local]  '
                          '"$request" $status $bytes_sent '
                          '"$http_referer" "$http_user_agent" '
                          '"$gzip_ratio"';



     client_body_buffer_size   1024k;
     client_header_buffer_size 128k;
     large_client_header_buffers 16 16k;



     access_log off;
     server_tokens off;

     sendfile            on;
     tcp_nopush          on;
     tcp_nodelay         on;

     client_body_timeout   15;
     client_header_timeout 15;
     keepalive_timeout     5 15;
     send_timeout          15;

     gzip              on;
     gzip_static       on;
     gzip_buffers      16 8k;
     gzip_comp_level   5;
     gzip_http_version 1.0;
     gzip_min_length   0;
     gzip_types        text/plain text/css image/x-icon image/bmp;
     gzip_vary         on;


     output_buffers      1 64k;
     postpone_output     1460;
     client_max_body_size 8m;
     server_names_hash_bucket_size 256;

     open_file_cache          max=2000  inactive=20s;
     open_file_cache_valid    30s;
     open_file_cache_min_uses 2;
     open_file_cache_errors   on;
     fastcgi_connect_timeout 90;
     fastcgi_send_timeout 90;
     fastcgi_read_timeout 90;
     fastcgi_buffer_size 512k;
     fastcgi_buffers 8 512k;
     fastcgi_busy_buffers_size 512k;
     fastcgi_temp_file_write_size 512k;
     fastcgi_intercept_errors on;
     fastcgi_ignore_client_abort on;

     # Load config files from the /etc/nginx/conf.d directory
     include /etc/nginx/conf.d/*.conf;

}


Any Ideas how i could resolv this?

Thanks!

Juergen