2005 S-Type naturally aspirated 4.2L engine, 186K mi, has been occasionally belching a big cloud of white smoke out of the exhaust. I think it is engine oil but I'm not certain. Most of the time there is no smoke or smell at all from the exhaust. The little bit of smoke that I have been able to smell really does not have much odor to it. Occasionally, when I first start the engine from cold, there is a small amount of visible smoke for a few seconds. If I get out, I can sometimes get a whiff. Occasionally, when I stop on the road and then make a turn, there is a sudden big belch of smoke from the exhaust that clears up completely after a few seconds. IDK if the turn has anything to do with it. It appears as if a teaspoon of oil suddenly got sucked into the intake. (Maybe from PCV path?) The smoke seems to come out equally from both exhaust pipes. The engine uses *some* oil, but I haven't figured out the current consumption rate yet. It *was* about 1qt/5k mi, but I think it has increased. This is a relatively new symptom. The problem started shortly before my last oil change, a few thousand miles ago. The engine seems to idle and run fine and there are no codes. The plugs are nearly new, 5K mi or so. I haven't pulled them yet to look for discoloration.
Has anyone seen this type of occasional oil smoke belching symptom? Any guesses better than random speculation as to what it might be? I'm looking for someone who has actual first hand experience diagnosing and solving this particular problem with a 4.2L in any early 2000's model.

 

More information is needed:

What engine oil is being used?

Is there any evidence of oil leaks?

Does the coolant level drop?

What type of driving is done, and under what conditions?

 

White smoke - oil? Something other than oil?

 

White dmoke is coolant. Oil leave a bluish ouf

 

I think oil. Based on the small amount of smoke that I can smell.
I think *not* coolant. It does not have the characteristic odor of ethylene glycol.

 

I have considered the possibility of a head gasket leak. It is possible, but I am suspecting something else at this point.
The engine has never overheated. I do not see any leaks from the sides of the heads, although such leaks could be hard to see.

What engine oil is being used?
Quaker State 5W30 high mileage full synthetic

Is there any evidence of oil leaks?
Not any engine oil that I can tell. I have some transmission fluid leaks from the cooler line flex hose couplings.

Does the coolant level drop?
I replaced the radiator about a year ago. Since then, I seem to have some minor coolant loss that I cannot locate. This started more than 10K miles before this exhaust smoke problem began.

What type of driving is done, and under what conditions?
Mostly highway, mostly using cruise control. Off highway, faster acceleration than most surrounding traffic, but mostly not very aggressive. I have been more gentle since the smoke problem started.

I have noticed something peculiar that I cannot yet explain, and I do not yet have enough data to say that it is not just a superstitious interpretation: It seems that the smoke belch occurs mostly when I make a left turn accelerating from a stop, and this is at very modest acceleration. So far, it seems that there is always a peculiar clicking or rattling noise that seems to originate from the left side of the engine compartment just before a cloud of smoke is emitted. The longer the noise lasts, the bigger the smoke cloud. The noise sounds like the pulsing of a small piston pump or the pulsing of an electric pulse modulated control valve. It does not sound like an exhaust leak, but this is just my impression, necessarily from the POV of the driver's position. I never have any smoke when the vehicle is stopped and idling unless I have just recently had a smoke cloud that is still clearing out. This is why it is difficult for me to get a good smell sample of the smoke. Normally, there is no smoke or smell at all to the exhaust when idling either cold or at operating temperature. Sometimes the pulsing is a single string of about 10 pulses in one second, at a steady rate even while accelerating. Sometimes it is more than one string in rapid sequence. The noise stops after I have completed the turn and continue with straight line acceleration. I do not always hear the noise before I see the smoke, but it could be masked by ambient conditions. When I hear this noise, it is *always* followed by a smoke cloud.

If this is actually a head gasket leak, the car will probably not be worth repairing, so I am trying to gauge its probable short term reliability to see how much more service I can get out of it. I will look at the plugs after a few thousand miles more to see if anything shows up. A head gasket leak should show one cylinder significantly different than the others.

 

Reading your described problem, I wondered if the issue was a failing oil control ring on one of your pistons. I'm uncertain this would fit with the scenarios you describe though.

Maybe try pulling a plug at a time & checking them to see ?

 

You mentioned that you use "Quaker State 5W30 high mileage full synthetic" oil. How many miles are on the engine? I don't recall you mentioning this...

 

I stated 186K mi in the first line of the opening post.

 

I will examine each plug after a couple thousand more miles.
I might be mistaken, but I think this engine uses two independent exhaust systems. I don't think there is a crossover pipe connecting the two sides. If they are indeed independent, a problem with one bank, be it a head gasket or ring problem, would cause smoke from just one side. I will look into this in more detail to confirm unless someone knows for sure offhand.
Also, the smoke production is highly intermittent and seems to be closely associated with that strange brief rattling noise. I have noticed this rattle followed immediately by a smoke cloud 3 more times since last post. The rate of the rattle is constant and independent of engine speed. I encountered it once at highway speed during mild straight line acceleration. In this case, the smoke cloud was sparse, consistent with the high exhaust volume at highway speed ~70 mph. At low speed, the smoke cloud is quite dense but does not cause any hesitation of the engine. In either case, smoke emission only lasts a few seconds each time.
I am a little suspicious of the fuel vapor purge system. I have temporarily disconnected the electrical connector from the purge valve to see if it makes any difference, for process of elimination.

 

A picture is worth 1K words. Snatched from the interweb... (Sorry for missing the mileage vis-a-vis my earlier post)

 

That does not look like my exhaust system at all.
I'll put my car up on a lift and look at it directly next time I have a chance. TY.

 

Have you checked the breather mounted on Bank 1 (circled in red)? The noise you hear may be from that component allowing oil to be sucked into the inlet manifold.

 

Oh, yes... that is the correct exhaust assembly. TY
Odd that the crossover pipe is downstream of the mufflers instead of upstream.

 

I thought that was the EGR valve. Is it actually part of the PCV system?
I will look into it. TY for the suggestion.

I looked it up. That is indeed the PCV valve.
RockAuto: https://www.rockauto.com/en/moreinfo...430961&pt=5052
I'm ordering one. The valve has never been replaced since I got the car at ~113K mi. I should have known. My bad.
I mentioned this as a possible suspect in my opening post: "...sucked into the intake. (Maybe from PCV path?)".


I stuck my finger into the outlet pipe of the PCV valve and withdrew this engine oil. I'm replacing the valve and we'll see what happens.

 

if the diaphragm it blows a ton of smoke