'97 Accord engine issues
 

My kids '97 Accord with the 4 cylinder engine is running like garbage. Frequently overheats if not careful and generally runs rough. I finally got the chance to look at it last night and when I removed the oil filler cap, while the engine was running, it was blowing what smelled like exhaust, out of the filler hole. I felt like you were putting your hand over the tail pipe. I've never seen anything like this before. Any ideas? My thought was there is a crack in the head.
Thanks,
Brent

Sounds like time for a compression test and might as well do a leak down test.