My 1998 SE occasionally has an annoying engine knock at cold starts. I have noticed a trend which exacerbates the problem. If, the night before, the engine is started and stopped for a short period of time, somewhere in the 10 to 15 second range, the knocking the next morning is loud and painful. The noise is almost to a point where you would think the engine is running without any oil. The knocking noise eventually goes away after about one minute while the car is warming up. During the knocking period I have also noticed a very different exhaust smell.

An example of a real bad scenario happened this week. On Sunday afternoon about 11:00 AM I started the car, pulled it out of the garage and turned it off. It ran for about 15 seconds. That same evening I started the car at about 10:00 PM and pulled it back into the garage. It ran for about 10 seconds maximum. The next morning I could barely get the car started. I had to hold the key in the start position for about 15 seconds to get the car turned over. Soon thereafter, when the car was chugging and knocking and bucking (my four year old son, sitting in the back seat was asking me, “Daddy, what is that noise? Why is your car doing that? Daddy, what is that smell?”. Even he noticed! It was bad. Anyhow, the car eventually settled down and ran normally after a warm up period of about one minute.

Is there something with the Maxima engine where short starts are bad for the engine? Is there something hydraulic going on? Does the engine require oil pressure or hydraulic pressure to set the cam or valves? Has anyone ever had or heard of this problem? Should I have this problem further diagnosed?

 

I experiance the same thing after a cold quick start and stop. Next morning the thing sounds like a diesel.

I think whats happening is during the quick start and stop you dump a good amount of raw fuel into the cylinders the night or day before which isn't burnt up. Now the next morning you have another cold start. Your ECU tells the fuel injection system to dump lots of fuel once again (a choke like condition) and you wind up with a few plugs that are fouled with fuel. This causes misfires and makes our cars sound horrable. Clears up in just about half a munute or until the burn becomes stable, plugs clear up and the misfire stops.

I don't think it does any harm to our engines because it's really not a lubrication issue, just a bad misfire at startup. Low RPM's and no load on the engine.

Anybody else have an opinion on this?

 

I use double platinum el cheapo autolite. just for reference.

 

I'm led to believe it's not the spark plugs. I just had a 60K dealer tune-up. They just replaced the plugs one week ago. Even with the old plugs (approx. 30K miles on them) the problem was still showing up.