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Old 01-19-2011, 10:41 PM
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Lopey idle on an 02' Overland / 4.7HO

I just put brand new OEM plugs in my 02' GC Overland. I was surprised that it did not remedy the lopey idle that was present before. Especially since the plugs I took out were gawdawful. I mean the gap on them was almost 3 times bigger than required. Honestly, I"m shocked it ran before. But, it ran okay --- but the idle was ...loping along. Almost like it was missing a cylinder. Under load it seemed to do fine. New plugs, no change.

It idle's around 550 RPMs. I can feel the "rough" idle in my seat. Can someone comment about how their 4.7HO engine runs?

Mine has 158,000 miles ...maybe that's the issue. Hope not.
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Old 01-19-2011, 11:53 PM
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Re: Lopey idle on an 02' Overland / 4.7HO

could be carbon build up. Do you have any kind of service history?
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Old 01-20-2011, 05:45 AM
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Re: Lopey idle on an 02' Overland / 4.7HO

Many times rough idle is caused by oil and dirt buildup at the Idle Air Control stepper motor. Remove the resonator box and clean out well the throttle body idle air passage and also remove the IAC motor and clean it out well. If this doesn´t help, cleaning the fuel injectors as second.
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Old 01-20-2011, 08:17 AM
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Re: Lopey idle on an 02' Overland / 4.7HO

Not much service history past along. Will look into the IAC cleaning etc. Thanks folks.

Hey, Frango100 - what does your rig idle at?
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Old 01-20-2011, 08:52 AM
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Re: Lopey idle on an 02' Overland / 4.7HO

Went back through the only service records I have and it's not too telling. Oil changes, brakes, wipers, etc. Heated seat switch and the actuator doors. Nothing that - to me - would relate to the idle.
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Old 01-20-2011, 11:17 AM
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Re: Lopey idle on an 02' Overland / 4.7HO

^^^X2 on it possibly being the IAC. Take it out and clean give it a good clean. Do the throttle body while you're at it.

Here's a couple of pics of my IAC
Apologies for the crappy photoshop!

The part circled '2' is the IAC. The part labelled '1' is the connector. Disconnect the plug and the unscrew the two torx screws (T20) holding the IAC in place and pull it out...


If it's dirty it'll look like this...


Give it a good clean and re install. You should see a noticable result and hopefully a total cure

Should only take 10 to 15 minutes.
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Old 01-20-2011, 12:44 PM
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Re: Lopey idle on an 02' Overland / 4.7HO

^throttle body/carb cleaner ok to use on that?
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Old 01-20-2011, 01:29 PM
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Re: Lopey idle on an 02' Overland / 4.7HO

Throttle body cleaner should be ok, only take care to not let it go into the stepper motor, keep the plunjer with the head down when you clean it. Also clean very well the idle air passage, the halfmoon shaped opening under the throttle inlet, because that also gets quite dirty.
My 4.7 runs at 650 rpm when idling. Hey JPILK99, don't know if you changed all the oils and fluids lately, but when your plugs had gaps 3 times the new ones, probably the normal maintenance was not done that precisely. I would change all ASAP.
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Old 01-20-2011, 02:00 PM
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Re: Lopey idle on an 02' Overland / 4.7HO

Quote:
Originally Posted by Frango100 View Post
Throttle body cleaner should be ok, only take care to not let it go into the stepper motor, keep the plunjer with the head down when you clean it. Also clean very well the idle air passage, the halfmoon shaped opening under the throttle inlet, because that also gets quite dirty.
My 4.7 runs at 650 rpm when idling. Hey JPILK99, don't know if you changed all the oils and fluids lately, but when your plugs had gaps 3 times the new ones, probably the normal maintenance was not done that precisely. I would change all ASAP.
^^^What Frank said x2. Especially that half moon shaped opening. Mine looked reasonably clean until I blasted some TB cleaner through it. There was a lot of crud in it.
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Old 01-20-2011, 08:10 PM
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Re: Lopey idle on an 02' Overland / 4.7HO

If you're going to use carb cleaner on the IAC remove the red o ring seen in Aarons pic above first or it will grow to twice it's size.
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Old 01-29-2011, 07:03 PM
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Re: Lopey idle on an 02' Overland / 4.7HO

Thanks SO much, folks. She's idling/running a lot smoother now. Right at 650rpms.

I changed the oil. What else should I do:

Anti freeze
Brake
Differntials
Tranny

If you have some links/info on any of these I'd appreciate it. I don't know if I've done brake fluid before...

Thanks again!
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Old 04-20-2011, 11:07 AM
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Re: Lopey idle on an 02' Overland / 4.7HO

Quote:
Originally Posted by jpilk99 View Post
Thanks SO much, folks. She's idling/running a lot smoother now. Right at 650rpms.

I changed the oil. What else should I do:

Anti freeze
Brake
Differntials
Tranny

If you have some links/info on any of these I'd appreciate it. I don't know if I've done brake fluid before...

Thanks again!
'IF you've done all that. I think the next thing would be the Fuel Filter. Its the best and most inexpensive maintenance item.

My Jeep improved 1-1.5 mpg just from this change and it idles and starts better too.
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