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Old 07-08-2008, 04:31 PM   #1 (permalink)
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Default VCM Problem?

I have always found that the VCM on my '06 operated almost imperceptibly, except the occasional ANC groan. However I am in the middle of a vacation trip through the South and now notice some engine vibration whenever the engine is on 3 cylinders (mostly notice it between 60-75MPH on the highway). Almost feels like the active engine mounts are not working? Could be bad gas? Engine runs normal except for the vibration on 3 cylinders. No dash engine/warning lights either.

Anyone have similar experience? I am trying to decide if I need to have it looked at while out of town or just wait until I get back (1500 miles or so).
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Old 07-12-2008, 09:44 AM   #2 (permalink)
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So I took my Pilot in to a dealer to have it looked at. Of course they could not "duplicate the concern". But to their credit they did have 2 different techs drive it, scanned the computer for error codes and a supervisor put it on a lift and inspected the engine mounts. Conclusion was maybe bad gas that made the egine run a little rough and was noticable when only 3 cylinders were running.

Anyways, this experience has shed some light on the debate on this site about what exactly the ECO light means in relation to running on 3 cylinders. While driving on a flat FL hwy. at 72 MPH the ECO light stayed on constantly, yet the VCM cycled in and out repeatedly. I would estimate that while the ECO light was on, it actually only ran in 3 cylinder mode about 1/3 to 1/2 the time. However, at 63 MPH, it ran on 3 cylinders about 80% - 90% of the time the ECO light was on.
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Old 07-12-2008, 12:53 PM   #3 (permalink)
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The ECO light in your model year will come on and off with the 3 cylinder operation, however, they put a "delay" on the light. So it can go out and come back on without the light shutting off.

In the 09 Pilot, the ECO light means something different and isn't necessarily tied to VCM operation. It's more of a "engine is in efficient operation for conditions" light.

I think your dealer's explanation is plausible.
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Old 07-12-2008, 01:10 PM   #4 (permalink)
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however, they put a "delay" on the light

That's my point. There had been much debate about whether the light has just a delay feature or a function of efficiency or etc. What I am saying is from my "vibration" experience, it is not simply that the light has a built in delay. I found that the ECO light would stay on for a half hour or more with the engine running on all 6 cylinders and onlly occasionally running on 3 cylinders. In other words, on the '06-'08 models it is definetly related to overall efficient operation rather than simply VCM mode.
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Old 07-12-2008, 04:35 PM   #5 (permalink)
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Quote:
Originally posted by th10000
however, they put a "delay" on the light

In other words, on the '06-'08 models it is definetly related to overall efficient operation rather than simply VCM mode.
Not the case in my 07. The ECO light is only on when the VCM is in 3 cylinder mode. When it goes into 6, the light shuts off. I don't have periods of more than a few seconds of "ECO" after a switchover.
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Old 07-12-2008, 07:57 PM   #6 (permalink)
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The ECO light is only on when the VCM is in 3 cylinder mode.

How do you know that you are not running on 6 cylinders when the ECO light is on? Until I had this vibration issue, there was no way to know for sure whether it was on 6 or 3 cylinders. That is why there has been discussion on this board about what exactly the ECO ligth represented.
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Old 07-12-2008, 10:23 PM   #7 (permalink)
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Quote:
Originally posted by th10000
The ECO light is only on when the VCM is in 3 cylinder mode.

How do you know that you are not running on 6 cylinders when the ECO light is on? Until I had this vibration issue, there was no way to know for sure whether it was on 6 or 3 cylinders. That is why there has been discussion on this board about what exactly the ECO ligth represented.
Fair question.

When it switches to 6 it feels a bit like a downshift, but you can see there is no change to the tachometer speed. Even if it were just the torque converter unlocking, there would be a change in tach.

There is a distinct power difference between 3 and 6 cylinder mode. I can only accelerate under certain conditions in 3 mode. The limit is easily reached on flat terrain, if you try anything but very gentle acceleration. But push too hard, you can hear and feel the switchover -- again, almost like a downshift, a somewhat subtle downshift, but it isn't a downshift. It is much easier to keep it in 3 cylinder mode at 60-65 MPH than it is at 70-75 MPH.

You can also shut the ANC off using the radio easter egg (turn radio off. Then while holding 1+6 together press "on". Then release all 3 buttons. Then press 1 to turn ANC on/off. You have to hit 1 a couple of times to get around a test mode, detailed in a TSB posted somewhere else on the site). With ANC off, you can more easily hear when the engine is in what mode. I did this for a couple of weeks until I was convinced that the light coordinated with the mode.

A side note, I was also surprised how well the ANC worked. It really was most effective at slower speeds, between 45-60MPH, ESPECIALLY with the engine under load, like going up a slight grade, you can really hear the 3 cylinder "hum". Above 65 it seemed perhaps that ANC was needed less.
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