My 240z seems to smoke a lot if the car is revved up when it's idling or if the car is cold. Once the car is warmed up it doesn't smoke when it's being driven, but it still smokes a lot if it's revved up when it's idling in neutral. What are all the possible causes of this? I'm thinking it could be a slightly blown head gasket that is causing some water/coolant to mix with the oil.

Sounds like oil ring bypass to me (smokes white , black or blue ? ) just my 2 cents..

Yeah I was thinking the same. The smoke is white.

Changed the oil lately?

Steve

Don't necessarily assume ring bypass. It's certainly possible, but these cars are prone to head and / or head gaskets needing replacement.

I'd start there and work "down". Do you see any visible oil weeping from the seal between head and block?

Time for a valve job or honing of the pistons. Mine does the same exact thing. Bad rings, and valve guides are the colprit.

Dave

The oil is brand new. I changed it a couple of weeks ago when I first brought the car home. There's no oil seeping out from the seal between the head and the block.

Just on the offchance, did you put seafoam in the car?

Will

No I did not. I'm not exactly sure of what that even is.

It is a combustible fluid that cleans engine internals and smokes white like you can't beileve!

Will

Seafoam is great stuff. I always keep some in my garage.

What oil did you use?

When you pull the plugs what condition are they in? They can help pinpoint the problem.