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Discussion Starter · #1 ·
Hey all,

This is my first Jeep, first SUV actually. I have the 5.7L 4x4. When I fiirst got it, I couldn't even tell the engine was on it was that quiet and smooth. Now, at 4000 miles when I stop at a light I can feel a little vibration, nothing huge but like I said, it was not there originally so I'm wondering if something's wrong or after 4000 miles this engine just isnt meant to be as smooth as at 10miles.

Thanks.
 

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Discussion Starter · #3 ·
INTREPER said:
It can be lots of things.
1. throttle body is dirty
2. spark plugs are slightly out of gap
3. cheap gas
I will suggest 1 and 2 to the dealer next week when I go in for an oil change. #3 is unlikely since I put in 91 Octane all the time..maybe gas is bad, sure as hell ain't cheap though.:(

Thanks for the advice.
 

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I have a commander with about 13,000+ on it. I had a problem with rough engine idle as well, took it to the dealer and they hooked it to the diagnostic machine. Turns out there were a coulpe of vac hoses loose and they had to replace the idle control module. Get it replaced soon because it will start to stall.
 

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In regards to the gas. I know from experience with mercedes that you should not put in 91 octane unless that is what the vehicle is supposed to use. A higher octane in a vehicle made to use 89 does not help. The engine is configured to run on a certain grade gas...you might be running a little rich on air to fuel ratio. I'm no expert, but that's what I have been told.
 

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perhaps the HEMI is angry with you for not giving it enough throttle ;)

definitely have them hook it up to the diagnosticator 5000 at the dealership, it sounds like you have a bad sensor/idle control.

as far as gas goes...i ran 87 in mine for a while and the engine was fine...started running 89 in it and it's fine...it does suggest using 89 in the HEMI, and i will continue to follow their suggestion just because i like to follow the rules.

anyway, back to the gas...you need some crapppy gas to get a rough idle in most modern vehicles. has it done it over multiple tanks of gas from different stations? if so, you prob have a little gremlin somewhere in your vac system or idle control module.

might want to have them check the crank sensor (i'm on my second) as well.
 
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