If you enter on your passport as a tourist without telling them you have a PR card, you are actually trying to deceive immigration and they might not be happy with that if they find out. They may have your passport in their computer so when you cross, they know you are PR and they will ask for your PR card and suspect you have something to hide. This will bring their attention to you. If you have renewed your passport, they might not know but they might have your name and birthday on file.
If you do manage to get across the border without being noticed, you could stay in Canada for a full 730 days and then apply to renew your PR card but if your PR card is already expired when you arrive, you might have problems signing up for health care, getting a job, drivers license etc. If your PR card is still valid and you can arrange all these things before it expires, you might not need it again for the next 2 years.
However, like some of the posters here, needing to go to Canada to sponsor their kids, this will not work because it means they can not sponsor their kids for the next 2 years.
You can apply on humanitarian grounds, sometimes it's accepted but it can take a year or more to process.
A word of advice.. if you care about your PR, make sure you meet the residency requirements. To stay in Canada 2 out of every 5 years are hardly very strict requirements to meet.