3.7 has a rough idle - JeepForum.com

 
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post #1 of 13 Old 04-09-2007, 11:15 PM Thread Starter
gsxr150
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3.7 has a rough idle

Today I picked up my rental Jeep 3.7. I'm in love with the truck, but when sitting in drive I get a weird vibration at idle. I seems the rough idle comes on and off....like 5 seconds on and 5 seconds off. Is that normal for the 3.7?

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post #2 of 13 Old 04-10-2007, 12:46 AM
bull_blaster
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i had the same issue, switched to higher octane gas and never had the issue again, but at the same time NO this should not be happing.
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post #3 of 13 Old 04-10-2007, 04:48 PM
ennemme
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I had a 3.7L on a '03 Cherokee (Liberty) but never had this problem...

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post #4 of 13 Old 04-10-2007, 11:08 PM
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Not normal with my 3.7 might be the AC compressor kicking in and out.
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post #5 of 13 Old 04-11-2007, 11:03 AM
drewman141
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The Libby engine is a different engine then the GC 3.7. And I agree with Cliff, sounds like the compressor cycling.

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post #6 of 13 Old 04-13-2007, 05:12 PM
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is that good or bad for the AC compressor to be kicking in. (i'm a car noob)...mine does this as well

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post #7 of 13 Old 04-13-2007, 05:59 PM
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Quote:
Originally Posted by rooster p
is that good or bad for the AC compressor to be kicking in. (i'm a car noob)...mine does this as well
The Air Conditioning compressor should only kick in if the AC is running, and will do so from time to time as the refrigerant warms and needs compressing/cooling again. So this is normal and good.


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post #8 of 13 Old 05-08-2007, 01:19 PM
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Quote:
Originally Posted by gsxr150
Today I picked up my rental Jeep 3.7. I'm in love with the truck, but when sitting in drive I get a weird vibration at idle. I seems the rough idle comes on and off....like 5 seconds on and 5 seconds off. Is that normal for the 3.7?
It's hard to tell what kind of "bargain" gasoline has been put in a rental. It may just be totally gummed up. If you're going to have it for a while, throw in a bottle of Chevron TECHRON Gasoline Treatment, and run the snot out of it!
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post #9 of 13 Old 05-16-2007, 02:59 AM
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mine does that, and i still havent yet fixed it. mine was a rental too.


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post #10 of 13 Old 05-16-2007, 07:59 AM
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My wife's '06 GC also has a rough idle, yet I have '05 and do not experience the same rough idle, at least not yet. I do notice that once it has an oil change it does idle smoother. I try and use the STP fuel injector cleaner every 3 fill ups just to try and keep the injectors and the fuel system somewhat cleaner.

As far as gas, we both fill up wherever the gas is cheaper that day, but usually the same stations, so I don't believe it's a gas issue. As far as I'm concerned gas is gas, they all get it from the same terminals. I know I've heard it before that it differs from one brand to the next, but I worked at a gas station in my college days, and the owners also owned a trucking business where they delivered gas to independent gas retailers, basically what they do is they would call there terminals and find out who had the lowest prices, then they would buy from them, after all do you think the no name gas stations have their own refineries?
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post #11 of 13 Old 05-18-2007, 08:59 PM
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I've also noticed this in my wife's 06 3.7. I wouldn't really describe it as a rough idle though. To me, it's more of an exhaust drone or engine harmonic at that rpm. When it does it, if you pop the shifter up into neutral it will go away. Also if you just barely put the slightest pressure on the gas pedal it will go away. IMO, the in-gear idle is about 50 rpm too low.
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post #12 of 13 Old 05-31-2007, 09:48 AM
sw99
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Quote:
Originally Posted by drewman141
The Libby engine is a different engine then the GC 3.7. And I agree with Cliff, sounds like the compressor cycling.
Really? What is different?
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post #13 of 13 Old 05-31-2007, 11:13 AM
drewman141
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Sorry about that, I was thinking of the JK engine. The 3.7 in the GC started out as the KJ engine, they just made a lot of changes to it since then.


Quote:
Originally Posted by wkjeeps.com
Significant changes in the 3.7-liter include a revised cam profile and new valve lash adjusters. These changes improve the engine smoothness at idle. To ensure quiet operation, a new thick-wall composite manifold is new for 2005, as are structural improvements to the air box and resonator. The cylinder head has been redesigned, increasing the compression ratio to 9.7:1. The 3.7-liter now uses plastic cylinder head covers.

[SIZE="1"]2008 WK Overland HEMI - Modern Blue Pearlcoat
Fully loaded with slush mats of course.

MUST GO! 1994 Limited ZJ 5.2L V8 - Light Driftwood Satin Glow
It's a 94 5.2L Limited - trxus 33's on 15x7 steelies, 4.56s w/ front OX and rear trutrac, NP242 swap, novak shift kit, Kevin's ultimate 4.5" lift + ACOS, ARB front bumper w/warn M8000, rear tomkin machine bumper w/ tire carrier, kevin's hardore railz, kevin's ultimate tc skid, kevin's trackbar conversion, rusty's gas skid, flexalite efan, Kolak's performance ignition and brake upgrades. ViAir OBA, custom storage/sub box and I'm sure there's a bunch of other things I'm missing. Everything is a little over 3 years old with less than 10K miles. Looking to get around $4k.




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