MrPeepers

So 95 4Runner SR5, it seems every couple months, the idle slowly goes down to 400-500 or so and sounds like it's going to die. If I adjust the screw up to 750, it will be fine, sounds great, runs great. Then a few months later the idle is back down. I looked for a vacuum leak but couldn't find one. ALthough I hear a sucking sound around the intake like there is a vaccuum leak, but all hoses appear to be going to correct place and plugged in. Now if I unplug the larger rubber hose that has the L that goes from the valve cover to the intake, the motor dies right away. Is that normal? Anything else I can check? Hidden spots that may be leaking?

DanStew

I know my idle screw seemed real loose. I took a dab of RTV and put it on the edge of the screw and the throttle body to prevent it from moving

Wrenchinjoe

Cracks in the old rubber intake tube(s) getting worse? Gooped up EGR? I had to lower my idle considerably with the screw after I cleaned the EGR pipe that goes into the plenum. Just a couple of ideas.

OutlawMike

Try replacing the O-ring on the idle adjustment screw.

Screw it all the way in, counting the number of turns. Take the O-ring off and go to a hardware store, match up the O-ring, install the new one on the screw, screw it all the way in, back it off the number of turns you counted, then fine tune it from there.

Mine was doing the same thing, the O-ring dries out over time.

MrPeepers

Cool thanks for all the suggestions, I will try those tonight. So should the engine die when I unplug that hose? It seems like if that's the case then any air leak in the valve cover would be a vaccuum leak? Incluing the oil fill cap not sealing airtight? or valve cover gasket leaking?

OutlawMike

Which hose? Not sure what you are referring to.

MrPeepers

The one that goes from the driver side valve cover to the intake. If I disconnect either side teh car dies right away. Even if I halfway disconnect one side it sounds like it is going to die and the RPMs go way down like its a hue vaccuum leak.

OutlawMike

That is part of the PVC system. With it disconnected air is allowed to enter the throttle body without first going through the AFM. As to why it dies, I would have to think on that one a bit more. The AFM flapper may go all the way closed, as little to no air would be flowing through the AFM, so, the computer thinks that the engine is not running, stalled, so, it turns off the fuel?? Anyone want to postulate on that one?

Anyway, as far as the oil filler cap, it might run with the cap off, as there are some restrictions between the two (baffles in the top of the valve cover). I have never tried any of this, they are supposed to be there and closed up, so I leave them that way.

Good luck.

MrPeepers

Strange, I bought a new PCV valve at Pep Boys, and I don't see anything like this on my truck. The tube I am talking about comes straight out of the valve cover, goes to an L shaped plastic pipe that is hollow, then that plugs into the intake pipe right before it gets to the Throttle Body.

Wrenchinjoe

The PCV valve is on the passenger side valve cover on the 3.0, buried under the intake plenum. It can be replaced without removing the plenum with a long set of needle nose pliers, but is a real biatch to do. If you ever pull the plenum, replace the PCV and its grommet, as it is really easy then.

OutlawMike

As said above, the actual PCV valve is buried under the plenum on the passenger side. A nice design feature, to say the least...PITA!

The breather tube on the driver's side valve cover is part of the system, that is where the air is usually pulled down into the driver's side valve cover. The air typically travels down through the head, into the crankcase, then back up to the passenger side head and valve cover, then through the PCV valve, into the plenum, and then into the combustion chambers. The PCV is a variable choke on the flow. At idle it has a large amount of restriction, as vacuum is high in the plenum and flow would be too high without additional restriction. As vacuum decreases in the plenum, the PCV adjusts to offer less restriction to increase flow. At wide open throttle, with little vacuum, the flow can actually reverse and go in through the PCV and out through the breather tube. That is how the throttle body gets all dirty and gummed up, reverse flow through the PCV system.

All that from two tubes and one valve...

MrPeepers

Ah the other side. That explains it, thanks guys. Yeah I hate that side, there are still spark plugs on that side that I haven't replaced because i don't even like looking over there. I will try the needlenose trick since I already bought the new PCV.

Thanks again!