Hi Sidney & Glory,
I think the problem is not with HSRP and its configuration. because,
1. standby 1 preempt delay minimum 180 is The preempt delay feature allows preemption to be delayed for a configurable time period (in our case 180), allowing the router to populate its routing table before becoming the active router.
so its ok
but still I will suggest you to add
1. priority on your stand by (defunately it will be less than 150 and it is best practice).
2. enable feature of preempt on both active and standby.
3. enable feature of tracking on both active and standby (you should track your WAN or next hop interfaces, again this for best practice).
4.and instead of using timers try to use FHRP which enables feature of BFD in HSRP (http://www.cisco.com/en/US/docs/ios/12_4t/12_4t11/hsrpbfd.html)
Again again, what i suggested above are the best practice config tips.
Now come to the point, As I told , I do not suspect with HSRP configuration.
I am suspecting issue with one important thing you have mentioned above is that CPU utilisation. (But you have not mentioned router, standby or active)
You have mentioned that the in time suddenly you are getting spikes in utiliston.
First you have to fix this issue.
Because, due to high utilisation your processor is not able to process packets and it is getting dropped and hence router is not able to send control packets and hence standby is not recieving control packets and attempting to become Active.
To do this, you can use
CPU utilization for five seconds: 0%/0%; one minute: 0%; five minutes: 0%
here importat part of output is CPU utilization for five seconds: 0%/0%
left most % is your CPUs overall utilisation and rightone is your Data plane or forwarding plan utilisation
By subtracting right one from left one you will get your control plan utilisation.
Ideally, Control plan utilisation is very less say 15-25%
But if you are getting high CPU utilisation you have to check why it is?
If it is no because of control plane and due to forwarding plan that you have to check on which interface you are getting excesssinve traffic. (though this is lenghty process you have to do that).
One more thing I would like to advise you that, always try to keep same image/version file on same .