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Honda K24 VTEC system–oil passages

Home Forums Stay Dirty Lounge Service and Repair Questions Answered Here Honda K24 VTEC system–oil passages

This topic contains 3 replies, has 2 voices, and was last updated by Nightflyr * Richard Kirshy 2 years, 6 months ago.

  • Creator
  • #989594
    Rudy R
    Rudy R

    2009 CR-V, with K24Z1 engine. I have an issue with the screen on the VTEC spool valve (which is what the Honda parts system is calling the “rocker arm oil pressure switch”) getting blocked with crud after the CR-V is driven for about 10 minutes. What happens is that it throws the P2646 code. I found the bottom part of the screen filled with black crud, and ended up replacing the gasket/screen since the rubber had hardened. I let it idle for about a half hour. Then I took it for a test drive and again, after about 10 minutes and while merging onto the freeway, it started bucking and triggered P2646 again.

    I have the spool valve assembly off right now and again, the screen had a little black crud on the bottom of it. My theory is that this crud is somewhere in the engine and, after it’s been run at typical RPMs of driving (vs. idling), then the crud eventually builds up and blocks the screen. When the engine is shut off, the oil drains back into the engine and washes some of the crud back in with it.

    The engine is otherwise solid. About 150,000 miles, burns maybe ½ to ¾ of a quart between oil changes, runs smoothly and quietly. The CR-V has hardly been driven for the past year. It is due for an oil change, based on time, not mileage, so I will be doing that regardless of what happens.


    There are two ports for oil passages on the side of the engine, and that is what my question is about. The top port is where the oil reenters the engine from the spool valve, presumably to trigger the VTEC system. The bottom port is what supplies oil to the spool valve and comes *from* the engine.

    Where does this bottom oil passage lead to? Does it come directly from the oil pump? Is it some other passageway? Reason I’m asking is that I am thinking of using something like Seafoam to gently backflush that passage and hope that whatever crud is in there will drain back into the oil pan. I thought of using compressed air, but that might just jam up the crud and block the passage. Otherwise, I could do an oil change and still have that crud lurking in the passage and plug the screen even with fresh oil once I go to test drive it again.

    The factory service manual didn’t show me how oil flows through the various parts of the engine, so I thought I would ask here. Mainly to see if it was safe to gently backflush that passage to get the crud well away from the VTEC spool valve and screen.

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  • Author
  • #989596
    Nightflyr *
    Richard Kirshy

    I wouldn’t suggest using compressed air and back blowing any passages.
    You have deposit build up with in the engine.
    That needs to be cleared out.
    My suggestion would be to get some inexpensive oil and a couple of cheap oil filters and some Marvel Mystery Oil
    Do a oil and filter change adding the recommended amount of MMO drive around for a day then drain and repeat until you see the the deposits stop showing up.

    Rudy R
    Rudy R

    I put in some Marvel and let it run 30-45 minutes (couldn’t drive it), changed the oil and filter, and it’s running fine now with no P2646 and no bucking. Drove it for about an hour yesterday with some hard pulls and the issue is gone.

    I still would like to know where the oil passage gets its oil from though. The Honda service manual doesn’t get that in depth of telling us where the oil is sourced.

    Nightflyr *
    Richard Kirshy

    Sorry, but Hondas are not my long suit so I can’t say for certain where the oil passages paths actually run.
    My guess is either off the main crank or cam.
    An oil pump only produces volume not pressure, Oil pressure is created by a fluid flow restriction in the outlet line of the pump, not by the pump itself.

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