I had a '79 VW Dasher (remember those?) years ago that someone sold me real cheap ($100) because it was smoking exactly as you described. They thought it was going to blow up any second even though it laid down a pretty impressive smoke screen. The cause was a valve cover vent line that was supposed to be attached to the PCV valve was instead attached to full intake manifold vacuum so it sucked all the oil out of the top of the head and burned it. Rerouted the line to the correct point, replaced the plugs and all was good. Sold it for $2500....

 

57loboy,

I feel much better knowing I am not the only one who has experienced this problem. I am happy that it was a minor fix, I was prepared for the worst, exactly what you said "They thought it was going to blow up any second even though it laid down a pretty impressive smoke screen."

I have been reading the different forums here and am learning a lot.

Thanx everyone!

 

I think I have had exactly the same thing happen to me today, and having looked around for the possible answer, and the strange coincidences of the same thing happening in the same way, I felt compelled to share my experience.

I too very stupidly forgot to put the oil filler cap on and went for about a 11 mile drive before accerlerating enthusiastically and had never seen to much smoke come out of the exhaust... Took it steady and no problem, arrived at my destination a further 4 miles on and check under the bonnet to see the oil cap was off.

It's back on now and still having issues with the smoke, I drove it around the block, so to speak, and will have to drive it back home later.

What are the chances myself and the OP have had the same problem with forgetting the oil cap, the smoke issue, AND both needing a PCV as a result...?

XJ8 X350 4.2 87k - engine sweet as and still is, no warning lights, oil seems to be fine. The only thing was noticed lumpy start this morning but likely due to oil cap being off...

 

Just a guess but could his leaving the filler cap off have changed the crankcase pressure enough to make the PCV stick open?

 

Thabks for your response.

Could be exactly that... Just driven home, there was a bit of smoke on startup (not typical of the car) and nothing for the rest of the journey, even when I floored it to see if it would, and nothing when I started again after going via shop. Really pleased that the issue appears to have settled and I may not have to buy a new pcv after all... I shall update again when I next take the cat out to play.

 

Just a further update, car asbolutely fine now, no smoke, would never know there was ever a problem!

 

ding ding ding.
This is the correct answer and issue. Since you left the oil fill cap off you created a big vacuum leak and way too much air flow in the crankcase. Way more than the pcv can handle so it let oil bypass into the intake and this was your result.