Bad PCV causing Valve Seals to Leak?
 

Have a 4cyl 1996 Camry with about 150k on it.

Problem.
It's been smoking lately- a little bit on startup, but mostly after taking off after idle (like at a stop light) or accelerating hard. The smoke is grayish-white and smells acrid. I also put my hand behind the tailpipe when it was blowing and found tiny black particles in the smoke, so I'm pretty sure it's oil. When the smoking issue occurs, it pumps tons of it out (like a total smoke screen), but only lasts for about 10 second and then returns to normal. Besides burning oil, the car seems to lag a bit on power and is failing emissions (suspect catalytic converter shot).

Investigation.
Having spent quite a while researching this, I originally suspected the valve seals or guides were leaking. Also might have been piston rings, but I'm less suspicious of this and think that if bad rings were the case it would produce a steady gray plume (my issue is intermittent). Anyway, I began the job yesterday and found the following:
- pulled the valvecase cover off and found the quite a bit of sludge and carbon buildup inside
- found oil in the #4 spark plug well
- engine seems pretty gunky (lots of oil gunk on hoses/connectors around valvecase)

Given these symptoms, I check the crankcase seal and it looked fine. Also checked the PCV valve and found it to be clogged.

Tentative Conclusion
So here's what I'm thinking. Pressure builds up in crankcase because PCV is clogged shut. This pushes oil into the #4 plug well and causes slow oil leak to coat hoses/connectors near crankcase. Also suspect the pressure pushes oil through the valve seals/guides into the cylinders. Does this sound reasonable? Does smoking during idling and acceleration make sense with this conclusion? What in the world can I use to clean off the sludge from the camshafts?

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I have a 1995 4 cyl that had a similar problem with smoking while startup, and it was caused by a leaking head gasket. My PCV valve was clogged as well, but from what I hear, that happens quite easily. If the engine has ever been overheated, I would check the head gasket, especially if you found any antifreze in the oil, or exhaust gasses in the radiator.

Yeah, I tried the new PCV valve and now it's running great. I also had to replace the valve cover because the internal lines were clogged. Overall though, not too difficult of a job.

PCV Valve Causing Oil Leak
 

I had the same problem recently on a 1996 Camry. My mechanic (also my brother-in-law) works mainly on Toyotas and said that oil leakage on the I4 Camry is a very common symptom of a stuck PCV valve or a clogged hose to the valve and the resulting build up in pressure. The hose to the valve was very hard indicating that it was probably totally clogged.

Typically (and fortunately) the leakage is through the valve cover gasket, not the head gasket (which is much stronger), or the oil pan gasket. It can be difficult to see where the oil is coming from since the leakage is on the back side of the valve cover.

I was surprised that the clogged PCV valve did not cause the vehicle to fail the smog check or cause the Check Engine light to come on.