Jeep Vibrates A lot When In Gear (auto tranny)

jeepXcore

jeepXcore

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Jan 8, 2017
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Collingswood, NJ, United States
So I'm getting accustomed to my Jeep after owning it for a few days.

I noticed when I pop it into gear when I'm stopped(break pedal depressed or not), the jeep gets very vibratey. Once I start give it gas and start moving, it ceases, but the minute I stop at a light, etc. it starts again. It almost seems like my tranny is putting more stress on itself than it needs to. This does not happen in park either. It shifts beautifully(no hesitation, no slipping), so I don't think it's a bad transmission. I'm thinking maybe I should check the tranny mounts? Any thoughts?

Or is this just the way Wranglers are? I know I'm going from a comfort boarder-line luxury GTI to a rough and tumble Wrangler.
 
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A few things come to mind:

1) Motor mounts: yours could be due to be replaced.
2) IAC: you should try cleaning your IAC it since it's cheap and free. This may fix a potential rough idle and could even alleviate your issue altogether.
3) Possible vacuum leak: you could have a vacuum leak somewhere near the throttle body.
4) Nothing at all: it's possible that there's nothing wrong at all. It would be hard to tell without me actually riding in it, but if it's just a small vibration I'd just chalk it up to normal. If it's very noticeable and violent, then something is wrong.
 
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Reactions: Jerry Bransford
In addition to motor mounts being a possible cause, add the transmission mount as a possible cause too. Especially prone to adding to engine vibrations are when the OE rubber engine or transmission mounts are replaced with polyurethane mounts.

And it's also true what Chris said about the IAC possibly being dirty enough to cause such a low idle rpm that the engine vibrates more. The IAC (idle air control) is a small device mounted onto the throttle body that provides literally all of the engine's air when your're not stepping on the accelerator pedal. If the IAC is dirty inside, it can prevent the engine from getting enough air to idle smoothly. Cleaning a dirty IAC will restore it to proper operation 99% of the time.

This is what the IAC looks like... that plunger is moved in or out as required to meter the proper amount of air into the engine when it's idling. Too much air causes the rpms to be too high, too little air causes the rpms to be too low.

IAC.jpg

TB & TPS Sensor Locations.jpg
 
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I agree with what Jerry said about the transmission mount also being another potential cause.

I'd clean out the IAC first to rule it out. It's easy and free, and will at least let you know if you need to dig further to solve this potential problem.

Here's a procedure (I linked to it in my original post) on how to clean your IAC.
 
So, I seafoamed the Jeep via the intake manifold and gas tank(had a few cans leftover from my GTI, so I figured "what the heck?") Didn't solve the problem, but being under the hood, I noticed there's a hissing noise that sounds like its timed/cycled, the engine will be running smooth, but every 7 seconds or so, the hissing noise happens the car idles rough for a split second then goes back to normal, and the cycle repeats itself. This is also whats causing the Jeep to vibrate via the rough idle for a split second.

I'm starting to wonder if the Evap Purge Solenoid is going bad? No CEL or codes so far by the way.
 
Make sure the a/c is turned off while you're looking for the source of the hissing noise. Is your radiator cap leaking, not the right 18lb. pressure model, or not screwed down full
 
Chris said:
Make sure the a/c is turned off while you're looking for the source of the hissing noise. Is your radiator cap leaking, not the right 18lb. pressure model, or not screwed down full
Click to expand...

Lmao, I think it was that I DIDN'T have the heat completely turned off, I had the fan dial turned all the way down, but I didn't have the vent dial turned to the solid circle(I'm assuming that's the "off" position to cut heat/AC). I did that this morning and now the whole thing is noticeable quieter; I think the symptoms I was experiencing was just the extra strain from the belt that controls the heat/AC. Didn't realize you controlled the heat/AC from that dial...derp. Gonna check the radiator cap and clean the IAC this weekend regardless though.
 
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Ockham's Razor at it's finest!

Glad that it looks like you got it figured out.
 
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