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Old 05-18-2012, 10:45 PM   #1 (permalink)
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Default Rough idle after front mount replacement

Husband and I replaced front motor mount today on our 2003 pilot. Now there is a noticeable vibration when the car is idling. Any ideas as to what might have occurred?
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Old 05-19-2012, 01:30 AM   #2 (permalink)
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Does the 2003 have the active motor mount with a vacuum line attached to it or?

If yours did not have the vacuum line, does the new mount have a nipple for one?

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Old 05-19-2012, 05:31 PM   #3 (permalink)
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I don't believe the 2003's had VCM in any form. That didn't arrive till 2005 or 2006 did it?

Presumably you either disconnected a plug pack or a spark wire when you were doing the job, or conceivably the engine has been idling rough for a while but you couldn't tell because of the knackered engine mount. Mostly likely just something that didn't get reconnected though. How involved is that engine mount replacement?
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Old 05-19-2012, 06:32 PM   #4 (permalink)
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Does the 2003 have the active motor mount with a vacuum line attached to it or?

If yours did not have the vacuum line, does the new mount have a nipple for one?
My pilot does not have the vaccuum line but the new mount has the nipple for one. Took it back to the auto store where I bought it before installation and they said it shouldn't make any difference. I was concerned this might be a problem?
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Old 05-19-2012, 06:36 PM   #5 (permalink)
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I don't believe the 2003's had VCM in any form. That didn't arrive till 2005 or 2006 did it?

Presumably you either disconnected a plug pack or a spark wire when you were doing the job, or conceivably the engine has been idling rough for a while but you couldn't tell because of the knackered engine mount. Mostly likely just something that didn't get reconnected though. How involved is that engine mount replacement?
We checked to make sure we didn't dislodge anything after installation so don't think that's it. Replacing this mount was fairly easy once we got the placement of the jack just right under the transmission.
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Old 05-19-2012, 07:08 PM   #6 (permalink)
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My pilot does not have the vaccuum line but the new mount has the nipple for one. Took it back to the auto store where I bought it before installation and they said it shouldn't make any difference. I was concerned this might be a problem?
I believe that's going to be your most likely problem right there. In other news, if it were me, there'd be an auto store employee in a bit of bloody hot water right about now. Shouldn't be a problem my sainted aunt Nellie.


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Old 05-19-2012, 07:45 PM   #7 (permalink)
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I believe that's going to be your most likely problem right there. In other news, if it were me, there'd be an auto store employee in a bit of bloody hot water right about now. Shouldn't be a problem my sainted aunt Nellie.


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That would be my guess too. I bet the one with the vacuum line is stuck supper firm thinking that it is under full throttle and needs to stiffen up. Replace with the correct mount and I bet the idle smooths back out.
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Old 05-19-2012, 08:33 PM   #8 (permalink)
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Right, agreed, if what's I'm reading here ( Brake & Front End: The Complete Undercar Service Magazine ) is to be believed. Active engine mounts are allegedly soft when they have vacuum applied and stiff without. That would certainly explain the harsh idle our OP is experiencing. I'd like to read something more Honda-specific to confirm that, but as of right now I'm sticking with my suggestion to go back and pimp-slap your boy at the parts counter, then have his boss discount the hell out of the correct part.
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Old 05-19-2012, 10:14 PM   #9 (permalink)
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MOTOR Magazine Article | MOTOR Information Systems
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Old 05-20-2012, 12:53 AM   #10 (permalink)
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I put a "nippled" engine mount in my '03 intentionally to keep it from ripping through front mounts every 30,000 miles. Since the Pilot has no switched vacuum source to control the mount, the mount--used in the Odyssey-- is always in "firm mode" even at idle. If you want your buttery idle back, get the un-nippled mount, which is designed to be soft all the time.
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Old 05-21-2012, 05:58 PM   #11 (permalink)
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Wonder if it would be a good idea to just "upgrade" your mount. Throw a T on a vacuum line and run a hose down to it.
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Old 05-21-2012, 06:04 PM   #12 (permalink)
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Well, then it's going to be perpetually soft. The factory setup has switched vacuum. I was wondering if the manifold vacuum pressure varies enough between idle and WOT to allow a meaningful change in the stiffness of the mount, but I rather suspect not.

I'm not sure what, if any, price difference there is between the active and passive mounts. It stands to reason that the active should be more expensive but you never can tell.
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Old 05-21-2012, 06:51 PM   #13 (permalink)
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Oh, I didn't know there was a solenoid that controlled it. Never mind then. It will probably be too soft and you'll probably lower the life of it.
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Old 05-21-2012, 07:22 PM   #14 (permalink)
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Quote:
Originally Posted by theirishscion View Post
...I was wondering if the manifold vacuum pressure varies enough between idle and WOT to allow a meaningful change in the stiffness of the mount, but I rather suspect not....
At WOT there should be zero vacuum and lots of engine torque to the wheels. Without vacuum the mount should be pulling downward on the front of the engine to resist this torque. Though I don't know how the whole solenoid comes into play. Either way, it's probably best to get the correct engine mount.
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Old 05-21-2012, 07:28 PM   #15 (permalink)
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Found this interesting tid bit:

Quote:
Originally Posted by Popular Mecahnics
Honda was first to introduce a system that enlists the power of the engine management computer to reduce vibration at idle. The mounts are hydraulic with two fluid chambers. But these are connected by orifices controlled by a vacuum-operated rotary valve. When the computer sees idle speed or that the a/c has been switched on (the load of the compressor can roughen things), it commands a solenoid valve to allow engine vacuum to reach a diaphragm that, in turn, opens the rotary valve. This makes the mount softer, hence more able to absorb unwanted vibrations. If you've suddenly noticed that idle is not as smooth as it once was, the first thing to check is the vacuum line that runs down to the mount. If it's intact, pull the hose off the solenoid and find out if vacuum is present at the solenoid's nipple during idle with the a/c on. No? Then you'll have to refer to factory troubleshooting information for the engine management system.

Read more: Replacing Loose Motor Mounts - Popular Mechanics

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