Vibration while idling in neutral

[aherrmann13]

I have a 2021 Sahara Unlimited with a manual transmisison. I recently replaced the clutch with an ACT clutch (~2000 miles on it now) and replaced the engine air filter with a new OEM filter. Ive noticed I get a vibration when I start the car and its idling ~600 RPM. Once I start driving the vibrations go away, even when I'm back to idle in neutral. Car is at 45k miles right now.

I am initially suspicious of my DIY work but it doesn't seem to be related to the clutch. There is no change in vibration when I have the clutch pedal pressed. I did the swap with the car on a quick jack and for the most part had a bottle jack supporting the transmission once I removed the crossmember but its possible the stress on the engine + transmission when I was moving it around to access the stupid wiring harness on the top of the trans caused some issue with the engine mounts. I'm hoping to get some advice on how to debug this further.

I can feel the vibration in the steering wheel, seat, and armrest. Revving to ~3-4k a few times seems to make the issue go away, but this is a new vibration so I want to get ahead of it. Once the car is moving it goes away.

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[alphawolff]

So on first crank there is an odd vibration, but once you drive it *at all* the vibration never returns, even when you're back in neutral?

 

[aherrmann13]

So on first crank there is an odd vibration, but once you drive it *at all* the vibration never returns, even when you're back in neutral?

correct - once I get the car moving it seems to disappear entirely. Left this detail out of the initial post but the vibration happens *most* times I start the car but not every time. Seems to happen more often when the engine is cold but it has happened when the engine is still warm.


I am gonna test the following the next few times it happens
1) let it heat up during idle without moving the car
2) drive a very short distance and restart the car

 

[alphawolff]

correct - once I get the car moving it seems to disappear entirely. Left this detail out of the initial post but the vibration happens *most* times I start the car but not every time. Seems to happen more often when the engine is cold but it has happened when the engine is still warm.


I am gonna test the following the next few times it happens
1) let it heat up during idle without moving the car
2) drive a very short distance and restart the car

Best I can suggest is motor mounts, but very odd.

 

[rickinAZ]

correct - once I get the car moving it seems to disappear entirely. Left this detail out of the initial post but the vibration happens *most* times I start the car but not every time. Seems to happen more often when the engine is cold but it has happened when the engine is still warm.


I am gonna test the following the next few times it happens
1) let it heat up during idle without moving the car
2) drive a very short distance and restart the car

I'm experiencing something similar. Did you ever chase yours down?

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