When I start the car in the morning especially these cold ones, I have significant valve knock.

Is this OK? Is there any way to solve the problem?

 

Does this valve knock last only five seconds? If so, it may be caused by a leaky anti-drainback valve in the oil filter. This allows the oil to flow "backwards" through the filter and back into the sump. Then, when the engine starts, it takes 4 to 5 seconds for the oil pump to refill those empty galleries. During that time the valve mechanism clatters. Replace your oil filter. Try a different brand this time.

 

My wife and I have a similar thing with our 95 Maxima w. 83k miles. Lasts for about 5 minutes. Sounds like valves but I don't really know what it is.

Had it in the shop the other day for the check engine light (bad front O2 sensor) and an oil change, and I had them look into the clattering sound while they were at it. They suspected it was the timing chain. Also we've heard from a friend of a friend who works on Nissans that Maximas are notorious for needing new timing chains. My dealer quoted $1,900 for parts and (mostly) labor. Youch! We're just living it with for now.

I'm going to get a Haynes manual to see what's involved. I remember working on the timing belt whilst doing some engine mods on my 79 Honda Accord. Wasn't too bad to get to, but the Maxima is probably a different story the way the engine is packed in there.