Take him to an Emergency Animal Hospital!!!!! They can die from eating chocolate!!!!!

I had a cat that I got when I was 5 yrs old and I am now 23, my parents just had him put down about a month ago die to the same symptoms. The vet told us that our cat had, had a stroke while my parents were away at the beach. I'm very … Read more

Or could be that the dog is having an allergic reaction

Sounds to me like a piston rod could be or beginning to break.  Has the engine ever been over revved or anything?  I had the same problem on my 1991 honda civic, thats what it turned out to be.