Occasionally the engine feels significantly rougher and louder when passing 3-4K RPM, almost like an additional fan or A/C compressor has come on. It does it even when the A/C is off, though. It probably happens 1 time out of like 20 acceleration runs. The car runs perfectly fine and there's no temp. change or other warning. If it's normal, what is it?

 

Are you on the gas more when it does this ? At 3-4K with little throttle it is pretty quiet. But, lean into the throttle to pass and "oh man" I love that sound and feeling. More air, more gas, more noise.

 

if it's not happening everytime, it's probably not normal. Sadly, if you can't reproduce it, the dealer won't do anything unless a error code pops up through their scan.

Is it happening at/near 4100 rpm, by any chance?

 

It really feels like you would imagine it did if it was running on 5 cylinders, but that would have to trigger the check engine light, no?

It's a constant roughness & change in sound throughout the whole rev range, but noticable more when I exceed 3-4K. Maybe a sticking VTEC solenoid? Something with the A/C compressor clutch?

Whatever it is, if it isn't normal, something will eventually break for the dealer to repair, I guess. You're right when you say that they won't be able to duplicate it.

 

That's weird. All I can say is that my 6MT has done nothing like that. Seems like I certainly would have noticed.

I'll pay more attention on my way home tonight, and see if I can duplicate it.

 

Mine is a little rumbly at idle but smooth as glass after that. I do sometimes notice something cycling on and off (like an AC compressor) but I have never payed enough attention to the circumstances. I'll see if I can narrow down the power range.

Don

 

Sounds normal. The Honda V6 is not an inherently balanced configuration and does not have balance shafts (at least from what I can tell in factory service manual). All that being said however, you will be hard pressed to find a smoother V6.

In-line 6's and V12's are inherently balanced configurations. Some balance shafted fours are very nice, but their power pulses tend to be more annoying than V6's. Balance shafts rob HP, so not having them is a HP advantange.