| c3uo |
So I bought my 2008 MDX slightly used about 1 month ago. It has 9000 miles, of which I've driven approximately 2000 miles.
I am very happy with the vehicle overall. The build quality is great with the exception of the gas cover door (this board has me out checking every body panel, etc.).
I do have two concerns which I'd like some feedback. I do not have a local dealer (closest dealer is 300 miles away), so I can not just stop by and compare my MDX to one at the dealer.
1. The engine noise when accelerating seems fairly high. It's sort of like exhaust drone at 2000 to 3000 RPM. My other car is an E90 BMW, so it's tough to compare to the smooth inline 6. It does seem louder then our old Highlander was. On the highway you would never notice it, and I checked the exhaust, etc. I think it is the nature of the beast, but wanted to check. This is different then the 1400 RPM resonant frequency that my vehicle definately has, but I just make sure I do not drive at that RPM.
2. There is a definite ticking noise at idle. It is worse when cold. It goes away when you rev the engine. My father in law's Honda Pilot does not do this. It sounds like it comes from the passenger side of the engine. Sounds like it could be either valve noise, an air valve ticking, or some other emission control device on the passenger side of the engine. You do not hear it at all from inside the vehicle, but definately from outside (probably the noise is exaggerated as it bounces off the walls of my garage). Is this normal??
Just thought I'd ask. I expect these are normal (with slightly louder ticking given our colder weather). The oil was recently changed at the dealer when I bought it (although it's a half quart over full). I may switch oil brands to see if it helps.
Thanks! |
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| bamdx77 |
Hello,
I think some sight ticking is somewhat normal. I had a 07 and now have a 08 and I did notice some slight ticking but it is not audible from inside the car.
Do you have vibration around 1,300 - 1,400 rpm? That is the issue I am trying to get resolved. It is mainly in the gas pedal but can be felt slightly in the wheel.
Thanks. |
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| c3uo |
I definately have a vibration at around 1400 RPM. It's something I have learned to live with, but it is somewhat annoying since it occurs exactly at the speed I drive at around the city (~30 MPH). I generally drop it down to D3 around the city since it then revs up above 2000 RPM and the vibration goes away.
I'm pretty sure the vibration is normal. In rotating equipment dynamic analysis you sometimes pass through "critical speeds" where systems resonate and vibrations are amplified at key RPM. Generally designers try to ensure the first critical speed occurs above the normal operating range. I have no idea if this applies to an engine, but maybe Acura / Honda has a critical speed at 1400 RPM. My second theory is that the engine mounts or exhasut just do not dampen the vibration properly at that RPM.
Personally it sort of sucks that this engine or exhaust has this vibration. It is funny that I never noticed it during my test drives (I believe this was because I always accelerated the vehicle every chance I could during the test drives instead of just coasting in traffic). I still am happy with the vehicle though. My car vibrates in the gas pedal (which is funny since the engine is drive by wire). I do not feel it in the steering wheel. I would verify that your exhaust mounts are centered and that there are no connections from the engine which are transmitting the vibrations to your frame.
I do think this engine is not as smooth as a typical Honda / Acura. But it is also the largest they make at 3.7 L and it's funny how it smooths out to normal levels compared to other vehicles at 3500 RPM and up. This could all be caused by the exhaust though since the Pilot seems smoother at low RPM and both cars sound similar at high RPM (IMO).
Anyone else have any thoughts??? |
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| bamdx77 |
Thank you very much for your feedback. The really strange part about this is my 07 MDX had no noticeable vibration in the gas pedal but the 08 does. The other thing I noticed is when the car has been idling for a while and heats up, that is when just let the car sit, I don't feel it, or when it is snowing out and the underbody of the car is wet, it seems to go away. This makes me wonder if it is an issue with the exhaust. It seems there is a temperature range not connected with the engine temp where there is no vibration. I have an appointment with the dealer so we will see what they say. There are other owners with the issue. It is annoying because I drive at 30 a lot as well and that is exactly where the vibration hits.
quote:
Originally posted by c3uo
I definately have a vibration at around 1400 RPM. It's something I have learned to live with, but it is somewhat annoying since it occurs exactly at the speed I drive at around the city (~30 MPH). I generally drop it down to D3 around the city since it then revs up above 2000 RPM and the vibration goes away.
I'm pretty sure the vibration is normal. In rotating equipment dynamic analysis you sometimes pass through "critical speeds" where systems resonate and vibrations are amplified at key RPM. Generally designers try to ensure the first critical speed occurs above the normal operating range. I have no idea if this applies to an engine, but maybe Acura / Honda has a critical speed at 1400 RPM. My second theory is that the engine mounts or exhasut just do not dampen the vibration properly at that RPM.
Personally it sort of sucks that this engine or exhaust has this vibration. It is funny that I never noticed it during my test drives (I believe this was because I always accelerated the vehicle every chance I could during the test drives instead of just coasting in traffic). I still am happy with the vehicle though. My car vibrates in the gas pedal (which is funny since the engine is drive by wire). I do not feel it in the steering wheel. I would verify that your exhaust mounts are centered and that there are no connections from the engine which are transmitting the vibrations to your frame.
I do think this engine is not as smooth as a typical Honda / Acura. But it is also the largest they make at 3.7 L and it's funny how it smooths out to normal levels compared to other vehicles at 3500 RPM and up. This could all be caused by the exhaust though since the Pilot seems smoother at low RPM and both cars sound similar at high RPM (IMO).
Anyone else have any thoughts???
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| shootist |
OK- One by one-
There is commonly an exhaust drone at 1,400 or so. In the past, some posters had their rubber hanger dampers replaced, but that was the past. There was an issue with these getting too hard too quick, and causing a louder drone than what you're hearing in the 2008.
Now- engine under acceleration. There are two things happening as you really wind up past 3,500 rpm. The first is that the VTEC system shifts the valve timing at about 3,800-4,000 rpm. The engine tone changes nicely as the engine literally gets up on the cam.
The bigger change happens at about 5,000 rpm- the intake manifold changes shape, to boost intake charging. That's when the engine really snarls.
Of course, I've never heard those sounds, since I drive very conservatively. |
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| eujinc |
quote:
Originally posted by shootist
Now- engine under acceleration. There are two things happening as you really wind up past 3,500 rpm. The first is that the VTEC system shifts the valve timing at about 3,800-4,000 rpm. The engine tone changes nicely as the engine literally gets up on the cam.
The bigger change happens at about 5,000 rpm- the intake manifold changes shape, to boost intake charging. That's when the engine really snarls.
Actually, it's the other way around. At 3800 rpm, 2nd stage of the intake manifold is activated first. Butterfly valves open, manifold volume increases, more air gets into engine, etc. At 4500 rpm, VTEC kicking in and the fun begins. Of course, at this point the valves in the exhaust silencers are also wide open for maximum exhaust flow. |
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| shootist |
I was worried I got that backwards.
This is the first time I've heard about valves in the exhaust silencers- are they like muffler bearings? |
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| eujinc |
After some previous posts mentioning a dual-stage exhaust system in the 2nd gen, which from my service manual does not make any mention of such a system (the diagram looks like any 'ol conventional system), I looked up what we have and there is a writeup on the exhaust (and other tech goodies) on this site: http://www.hondanews.com/categories/714/releases/4235
From the description, looks like there is an exhaust gas-pressure valve in the resonators/silencers that are before the mufflers. The 1st gen has a single resonator and the dual resonators in the 2nd gen helps with freer flowing exhaust. Any hoo, the valve is designed to add back pressure in the low revs and keep things quiet. As the engine speeds climb the valves open more from the increased gas pressure, thereby allowing more exhaust gas to escape. The sound also increases especially when the second intake stage is activated and even more when the second VTEC cams are engaged. |
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| bamdx77 |
I have an update on the vibration as well. I took it to the dealer and they could not find any problems but I did notice the vibration slightly in the steering wheel of the demo car and loaner car during power breaking during 1,200 to 1,300 rpm. I noticed that my car does not do it when it is 55 degrees or higher outside. Very strange, unfortunately when I took the car to the dealer it was 60 out so you could not feel the vibration in the gas petal at that time which made a diagnosis difficult. Has anyone else noticed that outside temperature is a factor. That leads me to believe it is exhaust related.
quote:
Originally posted by c3uo
I definately have a vibration at around 1400 RPM. It's something I have learned to live with, but it is somewhat annoying since it occurs exactly at the speed I drive at around the city (~30 MPH). I generally drop it down to D3 around the city since it then revs up above 2000 RPM and the vibration goes away.
I'm pretty sure the vibration is normal. In rotating equipment dynamic analysis you sometimes pass through "critical speeds" where systems resonate and vibrations are amplified at key RPM. Generally designers try to ensure the first critical speed occurs above the normal operating range. I have no idea if this applies to an engine, but maybe Acura / Honda has a critical speed at 1400 RPM. My second theory is that the engine mounts or exhasut just do not dampen the vibration properly at that RPM.
Personally it sort of sucks that this engine or exhaust has this vibration. It is funny that I never noticed it during my test drives (I believe this was because I always accelerated the vehicle every chance I could during the test drives instead of just coasting in traffic). I still am happy with the vehicle though. My car vibrates in the gas pedal (which is funny since the engine is drive by wire). I do not feel it in the steering wheel. I would verify that your exhaust mounts are centered and that there are no connections from the engine which are transmitting the vibrations to your frame.
I do think this engine is not as smooth as a typical Honda / Acura. But it is also the largest they make at 3.7 L and it's funny how it smooths out to normal levels compared to other vehicles at 3500 RPM and up. This could all be caused by the exhaust though since the Pilot seems smoother at low RPM and both cars sound similar at high RPM (IMO).
Anyone else have any thoughts???
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