Ok well i spent the morning wrenching on my wagon, trying to find out where all my oil has been going. Todays task was also to stop the throttle sticking closed, and i saw this.

 

The inside of the plenum is covered in a dusty/oily crud, as ive never stripped down a FI car before i have no idea if this is normal after 260,000kms. So the questions are, is this where my oil is going? There are no obvious external leaks and the car doesnt smoke. Should i bother cleaning it? and if i should, how?

I know its not a subaru but you guys are usually good.

 

KELTIK

The problem may be due to a bad PCV valve.

[...]The inside of the plenum is covered in a dusty/oily crud, as ive never stripped down a FI car before i have no idea if this is normal after 260,000kms. So the questions are, is this where my oil is going? There are no obvious external leaks and the car doesnt smoke.

Cougar brought up a good area to consider; a stuck PCV valve (open or closed) can cause lots of engine problems. Even if the PCV is operating normally, it can create some "interesting" conditions.

 

I don't know what vehicle we're discussing, but if it's losing oil and it isn't leaking out, then it must be being burned, whether that's obvious at the tailpipe or not. With the mileage you mentioned, there could be significant blowby. If so, that could be giving the PCV system lots to contend with, and in addition to exhaust gases aerosolized oil might be being fed to the intake. On many cars, temporarily disconnecting the PCV at the crankcase end (valve cover, wherever) will allow any significant blowby that may exist to be observed.

 

On the other hand, there may actually be a slow external leak that isn't obvious when the engine isn't running or at idle. If the PCV system (valve, hose, etc.) has gotten plugged, crankcase pressure can build up. That can force oil out of places it might not normally leak; it will usually be worse at higher RPMs, meaning that it might lose a drop every so often on the highway, but not show up in your driveway.

I didn't have a major oil problem before taking apart my 2.2L. The intake manifold didn't look too much different than what I can see in your photo. Where you'd really want to clean things up, make sure you do it around where the throttle plate meets the manifold - usually a ridge of crud where it rests closed.

260k kms is a little over 160k miles, so yeah the engine is a tad old, but by no means done for.

 

I too vote for a bad PCV valve. Be sure to use OEM to replace it, do NOT use aftermarket.

Cheers guys, i'll get right on that pcv valve. Good call with cleaning the area around the throttle plate - thats what i was snooping around in there for. So should i leave it like this or take it off and blast with carb cleaner? And does this blowby just mean new rings needed?

 

KELTIK

You're in New Zealand, any chance you chug up steep grades at wide throttle openings?

 

If so, then the rapid buildup is normal because the PCV system becomes non-functional at WOT. Just clean it off periodically.

 

You'll probably get a lot of blowby oil in the front portion of your air-box too.

 

**** ******!

Wow good guess, yes i have to climb a pretty steep hill 2-4 times daily, probably using 2 mins of WOT each way. And also climbing another range near by which needs 10mins of WOT. The other vent from the valve cover which feeds into the airbox is clean. So i need a new valve - this ones sticking, and make sure to clean it off periodically. Thanks!

 

KELTIK

Memo to self: "Take note of any posts by Blitz".

Do NOT clean off the goo around the throttle plate. That's there from factory, and it seals the throttle plate when it's closed so the ECU can properly regulate idle through the IAC valve. Cleaning that goo out has caused many problems for some.

Well there was no goo on mine so not a problem, i had a play with the IAV while i was there and its workin perfecto. As for the oily crud in the plenum, To clean, or not to clean? That is the question.

 

KELTIK