thatsgr8

Have a problem and looking for some help. I have searched on here and found nothing to help out. 2011 G37 Journey 93xxx miles. I have a vibration I am trying to narrow down. No vibration at idles and steady around 600 rpms. Hard acceleration from a stop it picks up speed as normal. Gears shifting normal. During a drive I feel the vibration slightly. At about 50 mph 2200 rpm the vibration is very noticeable and resonating. Throttle response lags bad during hard acceleration while driving. Had two fuel system flushes from a local mechanic shop. They did the first one and did a terrible job so I returned for a second cleaning. Helped out a little but returned within a day or two each time. Did seafoam and that didn't help either. I am thinking spark plug change is the next step. Any thoughts what to check next? TIA.

Hugh Jorgens

Any check engine lights on?

thatsgr8

No CE lights at all.

Hugh Jorgens

Maybe have someone check this out. It could be a driveline issue.

For now, stop using "cleaners". If there's no CEL, then you can be almost certain that the engine is running properly.

thatsgr8

Only reason I think it is an ignition problem (i.e.spark or throttle body) is while driving and depressing the pedal hard it hesitates before accelerating .

Hugh Jorgens

Maybe one of your engine mounts is broken?

Diff mounts?

thatsgr8

I thought that as well but the poor response to the throttle is still in question. Thanks for your help though.

Said Amir

Try it in manual mode and shift the gears your self. See if that changes anything.

thatsgr8

I did try in manual, still had the lag.

BoomerSpeed01

Hesitation and vibration upon acceleration point towards the possibility of the torque converter wearing out. Although you'd especially be feeling the lag from a stop due to the work the TC would have to do to get the car moving... So unsure there.
My car at times has a similar problem to what you're describing. It's particularly bad while the engine is still warming up and shortly after the gage gets to and stays at running temp. Even though the coolant has reached running temp doesn't mean the entire engine block is at the same running temp yet. My theory is that the different temps in the engine cause compression issues and the engine just doesn't like this. I'm unsure why this wouldn't cause a CEL as it basically throws the car into limp mode under 3-4rpm depending on the car's mood lol
Next time you drive, try not doing any hard accelerations even when the gage shows you've been at running temp for 10 minutes.
I'm thinking about swapping over to a cooler operating temp thermostat. For one I don't want to overheat in the summer cause I like to drive the car pretty spiritedly, plus it could possibly help with this issue.

BoomerSpeed01

After about 20-30 minutes of driving you should be free to do whatever you want. Winter seemed to have made this issue worse as well, which makes sense if my theory is correct because the cold air would keep the outside of the engine cooler than the inside (for obvious reasons) where during summer heat soak is much more prevalent and keeps everything pretty hot under the hood keeping temps more even in the block.

thatsgr8

Over the weekend I changed the plugs and cleaned the throttle bodies. Hesitation is completely gone. Now the minor vibration. I am leaning towards motor mounts. Been researching that part.

BoomerSpeed01

Hmm, I had checked my TB's and they were pretty darn clean. I'll have to check the plugs.

Avery Madrigal

were your TB’s dirty ?

thatsgr8

Yes they were dirty. The local ripoff mechanic supposedly cleaned them twice. First initial, then I took the car back after removing the air breather tube and found black soot behind the butterfly. Now it runs great except for the vibration that I am assuming are the motor mounts. That is a job I am not looking forward to.