Oil in my my Intake, what could it be?

Hey guys I need help identifying what's causing this.

I bought my 1998 v6 tacoma with 173k miles, and it was well maintained.

They changed the oil regularly, the transmission, radiator, filters, etc... have all been done.

Today was going through some things in the engine, and I pulled engine air filter only to notice that there was oil at the bottom of the air box. None on the filter it's self, just some dried, possibly older oil at the base.



The oil was some what dried up. There was some old black crud, and a little bit fresh oil.

I pulled the elbow only to see that there was oil at the base of it as well.



The hose that connected to the manifold had oil too...



But the throttle body wasn't real bad.



What can be causing the engine to send oil AGAINST the air flow.

The previous owner did say that there was a minor oil leak in the valve covers, and that they had replaced the drivers side gasket, but did not get around to the passenger side. They did give me the valve cover gasket for the passenger side since they had already bought it, but it hasn't been installed.

BUT I don't think that would cause this. The truck runs great. I drove it up from Florida to Virginia, getting 18.5 - 19.5 mile to the gallon on mud tires, and not one hiccup.

Does anyone have any ideas please. Seems like it could be a big deal.

 

Oil in the intake frequently comes from the make-up air system. There are two connections to the crankcase (often through the valve cover) on most modern engines, one for the PCV valve, and the other for make-up air. The make-up air one will typically be plumbed into the intake system before the throttle body, but after the filter. In normal gentle operation, it usually lets filtered air into the crankcase so that the PCV valve doesn't draw a vacuum inside the engine. On hard acceleration, the MUA system lets excess blowby in the crankcase vent to the intake, so that it is drawn through the engine and burned.

Often the air that is expelled through the MUA system carries a little oil vapor with it, which can condense inside the intake (and throttle body, and intake manifold) and leave oil or oily deposits.

Older engines, engines operated in harsh environments, engines with failing PCV valves, and engines operated at high throttle for extended periods of time, tend to blow more oil into the intake than generic well-maintained new-ish daily drivers.

Summary: Check your PCV valve for good operation, and check your MUA system to clean/replace a filter if one is present in that system on your truck.

 

^^^^^^ check PCV system

 

Thanks guys. I'm replacing the pcv valve today and cleaning the oil out of so I can monitor it.


In the meantime, is it something I should be worrying heavily about?

 

Basically...no. It is a nuisance, but barely more than a cleanliness issue. If the problem worsens, it MAY be an indicator of worn rings, but if I were you I would simply monitor the situation and not worry about it.

 

Thank you.

 

My truck is doing the same thing but my engine was just rebuilt. My motor as well is runnign very good and I dont think I am losing power. I just was told it was the valve cover crankcase breather being clogged.

 

What is a MUA system??