Strange OBD II code on '06 Honda Odyssey van

[Spittybug]

P1078 Intake manifold tuning valve - long stuck.

WTF is a manifold tuning valve and do I care if it says it's stuck? Engine light is on but no other symptoms. Car runs fine.

[dmc6960]

Probably for a variable geometry intake manifold. At one powerband the air goes through one plenum to maximize power. Then at another powerband its switch to another plenum to maximize power. This is because intake manifolds are not 100% efficient through the whole RPM range. This give the engine two options to choose from for the best power/economy. If its stuck at one setting and cannot switch, you may notice a power or mileage decrease in a certain RPM range.

[Ron]

That makes sense.

But I don't get the "long stuck" part:
I poked it in and got, "P1078 Intake Manifold Runner Control (IMRC) System Malfunction (High rpm)"
[P1077 is low RPM]

Check for vacuum leaks...and be prepared to see what a Honda VOD looks like...It's probably the solenoid that's buried there otherwise.

[Spittybug]

Ugh.... Can't believe that a vacuum leak just materialized on the highway near Waco (unless perhaps it was Davidian in nature....hummm). I wonder if there is a solvent-in-the-intake-air type of solution to try over the weekend? I have an appointment at Honda on Monday. No real desire to start ripping apart such a modern engine. Too much plastic, covers, inaccessible screws/bolts, etc... There is an elegant simplicity to working on our "vintage" jalopies.....

[Dangermouse]

Maybe there is a tuning valve - long, and a tuning valve - short.

Not that this really helps.

[Ron]

I wonder if there is a solvent-in-the-intake-air type of solution to try over the weekend?Seafoam via the brake booster hose is the only thing I would try, but your O2 sensors may not like it...
FYI, my crystal ball said: hose leak, hose blockage, intake manifold tuning valve, intake manifold tuning valve actuator, wiring, ECM (In that order).

[Spittybug]

I'm remiss on closing this. We took it to Honda and paid the $75 "look at it" fee. Reimbursed if you have them fix what they find. Well, it turns out that a connector to the intake runner control valve had come loose and all it needed was plugging back together properly. While it happened about 500 miles into a 700 mile trip and I therefore find it hard to believe it was due to any previous work done, I have no other explanation. A couple of weeks earlier I had changed all the plugs and the back ones are really challenging to reach, so it's possible I banged something loose in the process.

So, good news was that it was the cheapest trip ever to the dealership at $75, the bad news was that I had to spend $75 for something so stupid!