I have a 2008 is250 awd and I noticed that I have oil coming out of the connector on the white/yellow piece on the intake plenum. I have attached a picture. What is this piece and is this normal? What could cause this? It’s even in the connector, will this cause any damage to the wiring? If I have to replace it, do I have to replace the whole intake plenum? I know I’m burning oil, goes thru about a quart of oil per 1000 miles. I’m guessing it’s cause of the piston and piston rings, not sure if that’s related.

 

Well, I'd start by adding a catch can for sure.

 

I don't think that piece is replaceable. You will most likely need a new manifold. It looks to be just glued in place. Yours probably just developed a stress crack in that area.

Is the check engine light on? You'd probably feel the car idle surge if it has a vacuum leak. Then again maybe the connector seal is not allowing air to be sucked in.

 

Well lo and behold. Just finished checking mine out on a 2010 AWD. Now I'm curious is to what this thing does? Anyone have any suggestions? My thoughts is an air intake heater?

 

That's the ACIS. Acoustic Control Induction System. It's a flap inside the manifold that's normally open, but closes during the low-to-mid RPM range, separating each bank of intake primaries, to lengthen the effective length of each primary while the engine is trying to generate peak torque. Insert Helmholtz argument here, too...I'm not buying that until I've seen what a 3.5l sucking through it does. Why put foam padding on the flap if you're trying to increase acoustic efficiency?

Anyway, your oil on the plug is coming from that bad boy being utterly soaked in oil ingested from the passenger vent into the intake tube and--mostly--the vent from the back of the driver head into the intake manifold itself, directly behind the throttle body.

Both of you have extreme carbon buildup as a result, I'd bet.

To fix it, pop the intake off (it's all connectors, 10mm bolts and 5mm allen), use your carbon solvent of choice liberally, and a roll of paper towels. Pop off your Swirl Control Valve Assembly (more 10/5mm, plus the plug at the back), clean that thing up (it WILL need it), and if you want a bad day, shine a flashlight down into the intake ports on each head. Carbon solvent, bent up coat hangers hammered into scrapers (Ft. Benning style), bottle brushes under 1" od--and if you're impatient AF like me, a brass .50cal bore brush in one of those flexible Otis "cleaning rods" chucked into a drill--will be your best friends for a whole weekend. My first attempt was to media blast it, and honestly, that was dumb.

It's really not difficult. Once you've done it twice, you've done it a thousand times. It might cough a few times at restart from carbon-laden solvent getting burned off. Don't forget to plug your MAF back in at the end of all it...I've forgotten that THREE TIMES now. To fix it "for good", each head vent needs a catch can to keep oil vapors and combustion residue from getting into the intake tract.

 

Isn't the ACIS part of the lower intake hence the butterflies on that part of the manifold? As for carbon build up I have none.

lol I've already done it a few times with seafoam. Took off the intake uper and lower to check. The valves are clean as a whistle. I did have to knock off some left over with a long screwdriver. Then blew it out with compressed air.

So I'll seafoam it again to prevent it down the road.

While we are here about this contraption. I've been chasing what seems like a ghost.

Last few months has been reading LTFT bank 1 trims -10, -14 rich on bank one at idle.

I've checkd for exhaust leaks , vacuum leaks to above and beyond SMH. Fast forward today messing, and cleaning the connector with oil. Now my bank 2 is reading the opposite +10, +14 LTFT. While bank 1 has corrected itself back to 0.

While under load all trims are near zero. Within acceptable fuel trims. Once I let of the accelerator. The LTFT fuel will bounce back up to the given numbers above. Depending which bank is seeing the issue 1, or 2.

At this point I'm at a total loss. It's wired that it will only affect 1 bank at a time. While it goes into its Dr. Jeckle and hyde mood.

 

The Swirl Control Valves are the butterflies you speak of. To have oil seeping through the ACIS plug, you have to be ingesting a decent amount of oil vapors.

Ah, this would be why you don't have any visible buildup, but I dare you to take a bent-up coat hanger and scrape the walls of the primaries closest to the valve, most inboard to the engine. There's supposed to be a clear tumble cut cast into the short turn, but it's been clogged up to the point of nonfunction on the five 4GR heads I've played with. Cleaning the tumble cuts out has a slight seat-of-the-pants effect between gears; it takes less time/fewer RPMs for the engine to feel like it's breathing again.

My habit is to feed a whole can down the brake booster tube every couple of oil changes, stalling the engine out with the last bit, then letting it cool. Always looks like I'm invading Poland for ~20mi after I do.

I still do this, even with the oil catch cans. The OCCs seem to catch more combustion residue and let oil pass more freely than I like. I'll be using an inline fuel filter between the OCC and intake manifold to ameliorate that.

Do you have oil on the little o-ring-type seals between plastic intake and SCV plate, or is one of the foil-type gaskets under the SCV plate going to the heads compromised? Just my first out-the-butt guesses.

 

No oil on the o rings I've pulled off the manifolds about 4 times over the course of my ownership of the car. I installed new OEM gasket under SVC Plate to head. Then at a later time I went with a MAHLE gasket it seemed slightly thicker. Same scenario so far on fuel trim bank 1. Decided to do an ECU reset this past weekend. Let the cooling fans come on, and my bank 1 LTFT sits at -5, -7 at idle so far. Under load they will be close all close to 0. Occasionally bank 2 will go lean +3 LTFT while Bank 1 will go to 0 out cruising around.

Maybe I'm just trying to get the perfect fuel trims LOL.

 

I've done a bunch with the crank vent...least helpful of all attempts was to connect both heads to the same OCC that then went to the intake manifold. Foamed the oil, made an eerie sound like a vacuum ball about to quit, and kicked all sorts of codes unrelated to the systems I was playing with. Venting to atmosphere kicks codes and keeps your rings from sealing as well, leading to diesel-engine-levels of oil fouling. I can only imagine what the walls of our particular engine's cylinders look like with the amount of blow-by this thing's always had.

 

Found the SCV stuff here on Toyota engines. Not sure if its been posted before.

I've seen on my old GS400 it was activated by vacuum, and an actuator. So this electronic one really threw me off. More reading needs to be done on my part.

https://toyota-club.net/files/faq/13...engine_eng.htm

 

The only CC setup I'd ever use would involve a slash-cut "drain" into the exhaust. But hopefully I'll never need one on my IS350. Did one on my boosted Honda build many moons ago; worked great!