Intermittant smoke

My 02 ls v8 with 150k will sometimes let loose a rather large cloud of light blue smoke. This happend at startup a couple times last summer and is becoming more frequent but not just at startup. I have tried to run at highway speed and let off the gas (high vacum thinking valve seals ) and then accelerate trying to make it smoke, this dosent seem to always trigger the smoke cloud.When its getting ready to let loose a cloud theres a noise from underhood i will describe as a clatter(not the ball peen hammer sound of spark knock) it sounds more like a rapidly fluttering diaphram of some sort. Are thier any such devices on this car that could dump oil into the intake? I thought i read somwhere there was but don't have a clue what it would be for.

A puff of blue smoke at start up would be indicative a worn valve seals, but this time of year it's pretty common for condensation to cause a puff of smoke at startup as well. Is you car using oil between oil changes?

The Positive Crankcase Ventilation, or PCV, system could allow oil to get in to the intake, but the V8 does not have a PCV valve like the V6 LS does. I'm not sure what method it uses for ventilating the crankcase though.

-Rod

we have the same car and coincidentally the same mileage. i posted the same concern. if the valve seals are bad i would see this happening more often right? ...but its happening like once every three months, and when it happens, its a significant amount of thick light blue smoke. It only happens when the car is cold, i.e. sitting in the garage overnight. i don't recognize the odor of the smoke.

... but the V8 does not have a PCV valve like the V6 LS does. I'm not sure what method it uses for ventilating the crankcase though.

-Rod

The V8 does not have a PCV valve, but it still has a PCV system and it works the same way as any other car. The check valve is there to keep backfires from igniting the crankcase. The V8 guarantees by design that this won't happen, so no one-way check valve is needed. (No, I don't know how the design guarantees it.)

we have the same car and coincidentally the same mileage. i posted the same concern. if the valve seals are bad i would see this happening more often right? ...but its happening like once every three months, and when it happens, its a significant amount of thick light blue smoke. It only happens when the car is cold, i.e. sitting in the garage overnight. i don't recognize the odor of the smoke.

Do you get any kind of clatter type noise with yours?

we have the same car and coincidentally the same mileage. i posted the same concern. if the valve seals are bad i would see this happening more often right? ...but its happening like once every three months, and when it happens, its a significant amount of thick light blue smoke. It only happens when the car is cold, i.e. sitting in the garage overnight. i don't recognize the odor of the smoke.
I'm thinking the same as you if it were valve seals it should be always sucking oil in every time it idles or when you let of the gas.

I'm thinking the same as you if it were valve seals it should be always sucking oil in every time it idles or when you let of the gas.

Perhaps it only happens when a particular valve is in a particular position when the engine stops? Also, are you sometimes parked on a different slope that might make the oil more or less likely to pool around some of the valve stems?

Do you get any kind of clatter type noise with yours?

No it sounds normal.

Perhaps it only happens when a particular valve is in a particular position when the engine stops? Also, are you sometimes parked on a different slope that might make the oil more or less likely to pool around some of the valve stems?

yea but this has been happening intermittently over a couple of years. I park on level ground and if it were valve seals, i would think it would get worse over time and not stay the same. Interesting that its happening to another car.

Interesting that its happening to another car.[/quote]
Only ours that we know about because were on this Forum looking for awnsers but i would bet theres plenty more out there with the issue. It seems with there cars they all have the same issues, window regulators-check ,ac that chills one side and melts the other-check, sunroof drains that fill the door pockets up with water-check, heated seat broke- check, clock spring replaced to turn off airbag light -check again.

Interesting that its happening to another car.
Only ours that we know about because were on this Forum looking for awnsers but i would bet theres plenty more out there with the issue. It seems with there cars they all have the same issues, window regulators-check ,ac that chills one side and melts the other-check, sunroof drains that fill the door pockets up with water-check, heated seat broke- check, clock spring replaced to turn off airbag light -check again.[/quote]

this car is lucky that i still have a crush on it...:)

update.
I think the noise is definitely spark knock from when all the excess oil dumps into the intake air stream.
Wherever the oil is coming from it seems to be pooling up and releasing into the intake air stream i don't see any way that this amount can all the sudden run in past a valve guide. Yesterday it smoked some on cold start-up then I drove about 40 mile on rural roads with a few stoplights and didn't see any smoke until all at once in a town it belched out a cloud that obscured the people behind me's vision. Drove another 30 miles in the same type of conditions with no noticeable smoke then in the edge of a town again it belches out the huge cloud, you know when its coming because of the spark knock/preignition sound. I'm stumped as to where this oil can come from all at once.

Is it possible that rather than an oil burn cloud, it's excess fuel being burned off due to the misfire? How's the fuel economy? Are you needing to top off the oil regularly? While burning oil will have a bluish tint to it, it can be difficult to clearly distinguish between burning oil versus the gray of a rich mixture out the exhaust. The smell is quite distinctive between the two though. Maybe you need to have someone follow you and wait for the belch to help you determine if it's oil or fuel.

-Rod