Jace

Hi, first of all this is my first post here so I just wanted to introduce myself really quick. I have a 95 Subaru Legacy and I just love it to death. It has about 87,000 miles on it and I'm hoping to get several more years out of it before getting a new subaru. I'm honestly not a car guy, so that's why I'm turning to this community for some advice. Now to my problem, and I think it might be spark knock (if I'm using that term correctly). When I accelerate sometimes the engine will rattle a little, really hard to explain the noise. I live in Arizona and this only happens in the summer time and only during the day, at night the engine runs perfectly! By searching the internet and figuring out that spark knock happens only when the engine is under stress and especially when it's hot I'm fairly confident that's the problem. So basically my question is what do you guys (and gals hehe) think? Is it spark knock? And if so what options do I have to get it under control? Thanks in advance for any advice you might offer!!