I am a permanent resident of Canada, my current PR card runs from 2010 to 2015. I am currently in the UK, I have been here for 4 months since December 2012, now for various reasons I will be staying here in the UK until probably this time next year.
So my question is this, when I return to Canada will I get quizzed as to why I have been out of the country for about 1 and half years, and will it be a problem?
I am aware of the 2 years in every 5 rule, and by the time my card comes up for renewal in 2015 I will be over the 2 years required to maintain my residency.

Whenever I enter Canada I always seem to have to go into secondary immigration, so I am expecting the same to happen when I go back, so instead of having to go into all the various and personal reasons why I need to be in the UK for so long, could I not just tell them that I wanted to stay in the UK for that amount of time just because I wanted to live back in the old country for a while, and to be with family and friends. I will meet my 2 year residency requirement so is a "very good" excuse necessary?

As long as you meet the 730 day residency requirement or can meet it then you will be fine. The PR card expiry date has nothing to do with the 730 day residency requirement as it can be several months before you get a PR card.
Be calm and be patient if questioned by Immigration. Nothing to hide then nothing to fear. Answer their questions and you will be ok.

OK thanks for that, like I said its just a matter of me needing to stay here until next year for various personal reasons, but I know that I'll be quizzed when I get back. The immigration have always been fine with me in the past, so it should be OK.

I have been in the UK for 2 and a half years.I am planning on going in may and staying there for 2 years to keep my PR active.

No excuses required. You seem like you meet, or can meet, the 2 years out of 5 in Canada so beyond some questions from the guards to ascertain that I wouldn't be worrying. It won't be the inquisition by any means.

Thanks for your replies.
I like Canada but I also like the UK, and don't want to swap one for the other, I want to enjoy the best of both worlds.
The funny thing is I am a worrier, even though I have nothing really to worry about, I still tend to worry about being questioned by officials even when I have nothing to hide, but you guys have allayed my fears somewhat, and I will feel more confident when I do go back.