I have a 2002 maxima auto with 234,000 miles and has ran great until about two weeks ago. I have a knocking sound that come and goes at random also when it starts knocking it has a mist just like a bad coil but when it stops it runs like normal. Today I drove it maybe 2 mile and back home straight on the ramps crawled under as fast as I could while it was knocking and found that its coming from around the rear cat area. Has anyone ever had this problem if so how do I fix it.

 

Very common and there's no fix

 

No way this is common.

 

Your cat could be plugging up. There is a spring release bypass valve inside cats and if this opens and closes, it sounds like knocking. Happened on my wife's car.

 

Thanks the reply guys
Will that also cause the car to miss

 

It can make it seem like that because of a lot of back pressure in the exhaust system.