This was actually a tech help that I did, and the feedback on the fix made think it might be useful to re-post it here.

2010 Toyota Tundra 4.6 w/60,000 miles, customer recent purchase.

Engine smokes occasionally on start-up, and some when first driving. Seems to happen warm or cold after sitting a bit. Engine runs great except when choking on oil. Then clears out and runs perfect with no smoke at all. Has good even compression, and no blowby. No noises and good oil pressure.

I am 98% sure oil is getting into intake manifold, but I'm not sure where from due lack of familiarity with this engine. I have driven with PCV and breather hoses disconnected to see if any oil was blown out due to excessive crankcase pressure, and after a few hard runs, none was. I suspect oil is being sucked up into PCV system, but PCV inspection or replacement requires intake manifold removal. I'd like know where the PCV draws from and if there are known issues with oil collecting beneath it before I recommend pulling the manifold.

I checked for service bulletins and service info from AllData, and IATN archives. Nothing related found.

Thank You,

Tom

Updated on Nov 9, 2015 6:51 AM

I appreciate all the responses so far. Most suggestions are bad valve seals/worn valve guides. Let me give a little more detail. When this truck starts and you drive it, the amount of smoke can be very small, like you might expect with a valve seal issue, all the way up to enough smoke to mimic a very bad head gasket, and it will clear up within a 1/4 mile or less. So at times, it can be A LOT of oil smoke, or very little. But it always clears up and runs clean with no smoke.

Also, I have taken the truck down the road in 2nd gear and tached it up to 4500 and did a hard long decel. This will often show if valve seals are bad. I did this several times with no smoke whatsoever. I'm not saying that's 100% conclusive, but with the amount of smoke I see sometimes, I would expect at least a little puff during this test if it was the seals. I'm not ruling out the seals just yet, but the exact symptoms don't match valve seal issues I have seen over 33 years. However, my lack of familiarity with this engine means anything is possible for now.

I also removed the PCV hose, installed a thin cloth over the intake nipple, and reinstalled the PCV hose. After one start and short drive it was wet with oil, so I'm still fairly convinced that is where it is coming from.

Of all the replies, I was hoping one would describe the location of where the PCV valve sits, and if it is possible for oil to puddle in that area. So if anyone knows that info, I could use it. I would like to rule out the PCV system before going further as that is where my suspicions lie at the moment.

Also, the oil is clean, about 1/2 quart low, (assuming the correct dipstick), and I have no idea of the viscosity except to say it is NOT 90W ;).

FIX posted on Nov 18, 2015 5:44:31 AM

Well, truck is fixed! Most replies were sure it was valve seals. Steve from Tennessee had the great suggestion of installing a pickle jar in the line between the PCV and intake manifold. After just an 8 mile run to town and back there was 2-3 ounces of oil in the jar, so I was convinced I was on the right track with my diagnosis that the oil and smoke was caused by some kind of PCV system problem.

I pulled the intake manifold and then the oil separator where the PCV is mounted and found the problem. The oil separator has 3 holes. One is where the PCV valve goes in, and two vapor entry/oil drain back holes. One at the front and one at the rear of the oil separator. When I pulled the separator, the front drain back pipe that the separator plugs in to was completely stopped up with sludge preventing oil return. This pipe is about 4" long and has two 90* bends, probably making it prone to sludge buildup, so we may see more of these as time goes on. I cleaned the pipe, and replaced the separator and PCV valve. The PCV was also stuck.

I'm not ready to say whether this happened because of lack of maintenance or a design flaw because I have not had anything else apart yet. Right now I'm suspecting a little of both, although clearly this thing hadn't been maintenanced well. But I wouldn't be surprised to see this again in the future on other vehicles because I think the two 90* bends in the front pipe make it prone to buildup.

Tom from Tennessee