Vibration Noise, while accelerating - DISAPPEARS WHEN SHIFT TO MANUAL MODE

[jrporras]

New to site. Appreciate help on this.

2008 MAZDA CX-9 - 85K miles.

Develops a vibrating noise - front end of the vehicle. Vibration is intermittent while driving in 3rd/4th/5th gears and at speeds of around 30-60mph. Vibration only happens while accelerating. Vibration STOPS when I take the foot off the acc pedal. Noticed that while it vibrates, the car revs slightly up.

Vibration never lasts more than a few seconds.

Notices that there is NO vibration while driving in MANUAL SHIFT MODE - in fact while vibration is occurring, shifting to manual mode stops the vibration immediately.

Thanks for help -

JR

 

[tkageals]

Hmmmmm......we might have the same issue. I would not call it a vibration though (maybe it's not the same as yours). My wife calls it "kicking". It's almost like several abrupt surges or shifts, just some kind of "buck" in the drivetrain while cruising along. I put it in manual and the problem went away but came back later. I have checked the fluid and it's full. Same as you, lasts for a few seconds and goes away. No warning lights on. Any idea what causes it? I can't tell for sure if it's coming from the transmission or the engine.

 

[tkageals]

I replaced all 6 coils and all 6 plugs at 94K miles. I am thankful to say that the problem is gone!

 

[tkageals]

Oh yeah....I believe that the reason you feel it in 5th and 6th but not in manual mode is that the torque converter is locked in auto 5th and 6th so you can feel the engine misfire. In manual it's not locked and that just makes it harder to feel the engine misfire. That's all based on what I have read on the web. All I can say for sure is that on my wife's CX9, new plugs and coils cured the problem.