Removed my plenium to clean the EGR and noticed on one side the intake runners were coated with oil while the other side was clean and dry. Noticed some smoke out exhaust on startup today as well. The intake manifold gasket was replaced by a mechanic about 3 weeks ago.
1989 Iroc-Z

pic isnt my car just as reference.

 

Is there a vent tube in the valve cover on that side ? Mine pops out some times.

Smoke = valve seals

 

I was thinking the same thing. There is no oil up in the plenum (and a leak big enough to cause a mess would certainly make for lousy running). Gotta be that breather tube or oil somehow, somewhere making it's way up from the valve cover on that side.

 

I think so, I pushed it down but I might have just bumped it loose moving hoses out of the way. So here is an actual pic of my car. The mechanic said my valve covers were backwards and said it wasn't an issue. Are they really backwards? It would be more convenient if the oil fill was on the other side I guess. The hose pointed to in the picture leads to the valve cover. When I take it off there is oil residue on the spout. Also there was no smoke on start up this morning, maybe intermittent. I'm a quart low on oil so its going somewhere.

 

I can't offer you much help but it's curious in that the oil residue is in the runners that supply intake air to the same side of the intake that the PCV valve is connected to.

FWIW, your valve covers aren't backwards. You're just running two driver-side valve covers.

 

The PCV valve is on the other side (right) this side pictured has the vent tube in the valve cover (the side with the oil).

 

The intake runners on the passenger side of the plenum feed the driver's side cylinder head; the head with the PCV valve in it.

Because the PCV valve is sucking crankcase fumes into the intake, the vent tube is where fresh air is drawn into the engine. There is some reversion of the intake charge so if the PCV is sucking in oil it could end up in the runners. There should be no oil (or maybe a trace of oily film) in the vent tube or hose. I'd check the PCV system first. Just a thought.

Reversion: I had an old F-100 with a 390 in it that lost a valve seat in No. 2 cylinder. I found bits of the seat the No. 3 cylinder when I removed the head.

 

My 128k mile runners and plenum were completely coated with oil/carbon/black crap. The PCV valve shoots into the pass. side runners, and the other tube(the one I'm assuming you're calling the vent tube that sucks in air) that goes from the passenger valve cover to the throttle body is for crankcase venting. Pull off the plate that says tuned port injection and you'll see a nice bit of oil in there. I'm surprised that both sides of the runners aren't coated in oil, including the plenum.

 

Whats the best way to check that the PCV valve is functioning properly? If the vent tube wasn't seated all the way could that cause a problem?

 

Yeah, it could. But first things first- even if the tube was just swingin' in the breeze, no oil should come out of it. The PCV is supposed to be sucking the oil vaports out the other side of the engine, the vent tube is the CLEAN AIR SUPPLY feeding air back INTO the motor on the other side.

Now, if the PCV system isn't working properly, those vapors will go the OTHER direction- up through the tube into the TB. Oil all over things, as you can imagine.

Your PCV valve (or hose) could be clogged up. I'd replace the valve on general principle (they're cheap). While you have it off, plug it with your finger and have someone fire the motor. You should instantly feel STRONG vacuum on the end of that hose trying to suck your finger in. If not, you have a problem with the hose (clogged, badly split somewhere, perhaps) and that should be addressed before installing the new PCV valve.

 

Ill give this a try thanks

 

Yep, what Damon said. PCV should have good vac, pull it while eg is running it should tap when you put finger over hole ...

Hose from PCV to plenum - feel it, my hose was split, replaced it and the PCV ... cheap fix.

 

It clicked and sucked the **** out of my finger. What else can I try?