Oil in the upper intake manifold ohv 4.0

[aaron88]

I have a 1996 ohv 4.0 and I'm getting a lot of oil in the upper intake manifold and the back of the throttle body was caked in grime any ideas as to what would cause this? PVC valve is new. I'm also getting a rough idle and a really bad mis too the point where the truck will sputter and jerk.


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[RonD]

Oil in the intake can come from 2 things, PCV valve sucking oil vapor in or Vent tube doing the same, cheap oil generates more oil vapor.
Or the EGR system, if rings or intake valve guide seals are leaking oil and it is being burn in the cylinders, the exhaust will be oil rich and the EGR system sends it into the intake when it opens.
Are you burning oil?
Do you have an EGR system?

Oil in the heads intake valve/intake area is from leaking valve guide seals, you can change intake seals without removing heads.

 

[aaron88]

If I'm burning oil it's not enough to notice in the exhaust or low oil levels. I've always put mobile one full synthetic in it and no egr system. PVC valve is brand new I replaced that today.


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[hilltopfarm]

I had this problem with my old 2003 4.0L SOHC. Enough oil for a paper towel to be completely soaked... I think in my case it was worn rings/valves...

 

[RonD]

Could have been there awhile?
From previous owner

Is it oil?
Upper intake has 4 "holes" that bring in "stuff" from the outside
Throttle plate, pulls in air and "stuff" from the air filter and Vent hose.

PCV valve, pulls in blow-by vapor(exhaust) and oil vapor from crankcase/valve cover

IAC valve, pulls in air from just outside the side of the upper manifold, usually it has a filter but not always.

Vacuum manifold, there is the Fuel Pump Regulator(FPR), EVAP system, Power brake booster.

 

[aaron88]

It's oil for sure, I'm thinking its just time to build a brand new 4.0 with a little bit of extra power. This one had 150k on it when we put it in I rebuilt the top end and left the lower end alone due to funds. But it's looking like ill be needing a new engine I'm guessing its getting up there because it has an excessive amount of blow by but it's strange because I can't feel a lack of power and when I did the top end it was all relatively clean for 150k not to mention I cleaned everything spic and span. I am just going to build a hot little v6. Step the compression up a hair, cam, port polish the basics nothing crazy just a little something extra I already have a 1999 ohv 4.0 sitting in the garage. My biggest issue is if I'm going to use that with my current harness which is a 95 cut down to bare minimum. Keep in mind this is in a 1988 ranger and smog isn't an issue.


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[RonD]

Computer can be an issue if cam is changed, so check out how far you can go without "chipping" the computer.

A vacuum meter can give a pretty good indication of the ring condition, and is just a good inexpensive tool for diagnosing other issues.
Google: Engine testing with vacuum meter

 

[85_Ranger4x4]

It seems the first thing everybody recomends doing when they get a new sporty car (Mustang/Challenger/Camaro) is adding a catch can on them to keep the excessive oil vapor from collecting in the intake. It is rarely very much they catch but they do catch more than you think they would especially on a brand new engine. If nothing else it would be a way to visable keep track of how much you are getting.

It seems it would be a decent get-by-with band aid if you can't afford to put a new engine in the truck. To my knowlege it isn't all that common of a problem with Rangers though. A little bit is natural, but you get a little bit of buildup over decades and there comes a point where it isn't a little bit anymore.

I don't know why, if some of the newer PCV systems catch more of it, intakes don't have air moving as fast to keep it suspended or what. I have the simple $3 push in PCV on my well worn but non-smoker 302 and the intake is bone dry whenever I have the carb/intake off.