My 2001 S-Type has 110k miles on it and has started, occasionally pumping in blow by into the cabin; which usually occurs while at a stop light. It doesn't do it all of the time.

What causes this and what do I do to correct this condition?

 

I don't recall this out of some years of reading the forum. I don't think it will be blow by.

If it's a burnt oil type of smell then it's oil leaking and burning. Most likely on the hot exhaust - where else?!

See the FAQs about IMT valves, I suspect. DIY and fairly cheap if it is.

If it's not that, I guess PCV is next most likely. Then I guess EGR.

I hope you changed plugs at 70K
Or since, if not!

Have a hunt around the FAQs anyway as at that age and mileage you want to be doing various jobs (the infamous elbow, for one).

If you have trouble figuring the cause I'd check fuel trims next (an elm327 is good & cheap).

 

Yea, what JagV8 said if what you meant by blow by is the smell of burning oil inside the car.

A quick background before your search. The IMT valve is located in the rear of the intake manifold. The PVC system (like all modern cars) is a closed system unlike the early cars that vented to the air. So, PCV gasses are routed back into the intake. Because of this, oil condenses out of the gasses and pools in the intake. The IMT valve is at the lowest point so oil pools there. With age the gaskets (o-rings) fail and allow oil to drip down the back of the engine and onto the exhaust....hence "stinky smell"... Actually not a major issue and pretty easily fixed..

 

Best "Smoking" description/advice I've read yet...congrats to jagv8 and Jeff. Keep up the good work fellas.