Oil in the Intake Manifold
 

Today I took off my throttle body to clean it, because I've been chasing that throttle response after I put a few zipties on my throttle cable to tighten it up LOL.:sgrin:

It definitely needed it, I doubt it had ever been done before. Yesterday I cleaned the IAC as well, both were filthy.

When I had the TB off, I peeked into the manifold with a flashlight, and noticed it was pretty dirty as well, even with a small pool of oil in the corner (probably less than 1/2 a teaspoon if i had to guess)

My questions are: Is this a problem? Is this a common occurrence? How should I go about cleaning this? Does this have any effect on performance?

It will effect emissions but not performance.

All piston engines have "Blow-by"

When a cylinder fires some of the explosive pressure "blows by" the piston's rings, the cylinder's wall below the rings is coated with oil, the super heated blow-by gases vaporize some of that oil, and crankcase is filled with blow-by gases and oil vapor.
In the old days there was a vent pipe on upper oil pan or lower block pointed down at the ground, it would drip out oil all the time, venting the blow-by gases and oil vapor.

This of course was bad, environmentally, so engines were fitted with Positive Crankcase Ventilation(PCV).
Since crankcase and valve cover area are connected via the oil drain back holes, air from a valve cover is sucked into intake via engine vacuum and the Blow-by vapor is burned in the engine vs dripping on the ground.

All engines have blow-by, brand new out of the box engines, but as miles go up the blow-by increases and so does the oil vapor it generates, also cheaper oil vaporizes more.
In any case you will get oil vapor condensing in the intake because of its cooler surfaces.

With high mile engines some install a "catch-can" on the PCV system, and some new engines came with catch-cans.
Basically it is installed on the PCV hose and allows the oil to condense into the "can", which can be emptied, instead of the intake.
Catch-can doesn't effect the benefit of a PCV system, it just collects most of the oil.

But IMO at the point a catch-can is needed, engine burning lots of oil because of older rings, it is probably time to rebuild the engine.

The PCV valve doesn't work like most think.
It is CLOSED at idle, highest vacuum and lowest blow-by.
High engine vacuum pulls the PCV valve closed, as engine RPMs increase blow-by increases and vacuum decreases, so PCV valve starts to drop open and pull the blow-by into the intake.
If PCV valve isn't working correctly then you could be sucking too much oil vapor in.
People often shake a PCV valve to tell if it is "good", the telltale rattle means the valve inside is free to move........so engine vacuum can suck it closed at idle, not a definitive test, lol, but it does mean valve isn't stuck.
i.e. if PCV valve doesn't rattle then it is bad, but if it does rattle it doesn't mean it is 100% good

PCV system also has a Fresh Air Vent, a hose usually connected to air filter housing or air tube on intake, and then to valve cover.
This needs to be clean and clear, it helps condense oil vapor inside the engine, so PCV valve pulls in less oil vapor and more blow-by gases.

That's kind of what if figured from a little bit of research..

I'm not super high miles (142K) and have only run synthetic oil for truck's entire life.
I'm not burning any oil, so I think a rebuild can wait.
Is this an expected amount of blow-by condensation for a 22 year old truck?

So i just popped off the PCV, a white little ceramic piece with a ~3 inch hose connecting it from the valve cover (Driver's side, towards the back) and shook it. It rattles, wiped it off and put it back in. Then the Fresh Air Vent (hose between the Engine oil fill cap and Airtube) washed with soap and water then dried.
I will probably end up replacing the PCV anyway since it's like a $5 part..

But as for the manifold, would you just leave it as is? It seems like there are some ways to clean it without taking it off, which is the only way I'd consider cleaning it.

On the Seafoam website, they have this one treatment with the spray can where you basically stick the straw in just upstream of the throttle body, and spray the whole can in there while running 1000 rpm above spec idle, then let soak, and then drive around the block a few times. I'm considering doing this anyway, as it sounds like good easy way to clean and lube the intake and upper cylinders.


Have you ever done this?

http://seafoamsales.com/wp-content/u...e-Port-GDI.pdf

Putting any liquid into the intake of a running engine is dangerous
Google: hydrolock engine images

No, it won't clean the inside of the intake, the oil is there because air flow, even at 5,000rpm, doesn't move it from where ever it has settled.
Not hurting anything in any case.

The described Seafoam treatment is to clean carbon build up from the back of the intake valves and the inside of the cylinders.
There is nothing to "lube" inside of an intake or in the combustion chambers of the cylinders

Look at your spark plug tips, if they are blackish and get blackish after they are cleaned then you do have a problem with carbon build up.
This also causes pinging/knocking when engine is under load

If you don't have carbon buildup then don't bother with that type of treatment.
4.0l OHV never had carbon build up issues like the 3.0l Vulcan did

Yeah, don't want that to happen!!

Thanks for all your advice Ron, I'll stop worrying about the oil in the intake. Good to know that the Seafoam wouldn't have cleaned the intake.

I just changed my plugs 10K ago, one of these days I'll pull one out and see how it looks. But I doubt I have carbon build up, no knocking or pinging.