CitadelJeep04

I have an 08 Unlimited X. Auto trans. 3k miles. I've started getting this really bad vibration when the Jeep is at idle in drive. It goes away when i hit the gas to go, but every time i come to a stop in traffic it comes back. I've noticed its idling around 500-550 rpms, and it almost feels like the engine is on the verge of stalling, know what I mean? I just put 33" tires on 2 weeks ago up from the stock 225's, but I havent calibrated the speedometer yet. I need to change the oil for the first time too. I also just took the carpet out Friday, so am I just noticing more vibration?
Has anyone had any problems like this, or could it be any of the above problems that could be fixed?

themadpants

My first thought is that you need to have your idle reset. If it is idling at the low revs you mention, you are right in thinking its on the verge of stalling.

CitadelJeep04

What are the rpm's supposed to be at when at idle? They bounce back up to 750 or so when in park, but drop alot in D. Would the dealership charge me a lot for a reflash? Or is it a warranty thing?

rab986

Could be several things... plugs, wires, vacuum leak, idle stop solenoid etc etc. I assume you have no check engine light?

CitadelJeep04

Nope, no check engine light. I'll check the plugs and vacuum lines after work today. It also does it when I'm driving and the rpms go down to around 1000 when I'm doing 40 or so. Just vibrates like a mofo. If I was a chick I'd dig it...

cmpmacchia

Does it almost feel like a slight misfire? If so do a search I believe this a normal condition. Something about the engine not having balanced shafts. My engine started doing this at about 3000k as well. I don't even notice it now.
Normal resting idle in drive is around 600 RPM.

CitadelJeep04

This sounds alot like it. Like it either has bad gas or its trying to stall at low rpm cruising. The only other way I can describe it is like I'm driving a manual and I need to downshift?? Like its bogging down. But its an automatic...

l3itch

I have an auto too and mine started doing this at about 7,000 miles. It was right after I drove a really really long road trip, but I don't know if that had anything to do with it. I think it idles too low now. It's just really rough. I have been thinking about taking it in and asking the stealership about it, but I have been too lazy.

Let me know if you figure anything out.

JKGirl

Mine does this too...but my engine light comes on randomly...ugh. I told hubbo to just get the hemiand be done with it! LOL

greenamphibious

oh man if my wife even joked about that I would be driving to SLC!!!!