Rough Idle, Spark plugs, vacuum leak -
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post #1 of 5 Old 06-20-2013, 07:54 PM Thread Starter
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2001 WJ 
Join Date: Feb 2012
Location: Goffstown
Posts: 110
Rough Idle, Spark plugs, vacuum leak

Well I finally got around to changing my spark plugs. Turns out the previous owner had platinum's in it and they were pretty nasty. It was pretty easy to change them even the passenger side rear wasn't bad at all I just used two 3" extensions and a flex head socket wrench and it came right out with no trouble. The pain in the *** for me was after installing the new plugs the plug socket would get stuck & not come out, happened on 8! Had to climb up a grab it with a pair of needle nose pliers to pull it out.

So prior to changing my plus I had a fluctuating low idle. I changed the tps sensor, cleaned the intake, & the other sensor which I can't remember what it's called at the moment, but the problem persisted. I just assumed it was the plugs, and the plugs were pretty bad. While I was in there I noticed one of the vacuum connectors was dry rotted & cracked. so I replaced it.

So far so good, runs & idles like a champ. So before you go replacing sensors take a minute to check the vacuum connectors and you might save yourself a few bucks!


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post #2 of 5 Old 06-20-2013, 08:33 PM
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Thanks for info! Can you show which hose that was? I have been chasing a low idle especially when hot.

03 limited 4.7 H.0., Superchips, TM wire snip mod, K&N drop in with custom intake box. 265/70/17 TKO's
BDS 4" coils, KOR .75 rear spacers, Fox shocks, BDS adj LCA's, A-arm spacer, adj.track bar, quick disc. front links, extended rear links, dual SS, Addco rear sway bar.
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post #3 of 5 Old 06-20-2013, 08:54 PM Thread Starter
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Location: Goffstown
Posts: 110
It is one that connects to the intake, there are two hoses that connect, check them both
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post #4 of 5 Old 06-21-2013, 06:52 AM Thread Starter
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2001 WJ 
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here is a pic, it is the small ruber hose that connects the tube to the intake. The one closest to the firewall was the bad one on mine. Much to my dismay, this morning the low Idle showed up again at a stop light. It only seems to happen when in Drive and at a stop. If I shift into park or neutral the idle jumps right back up.....and it doesn't happen all the time which makes it more frustrating....

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post #5 of 5 Old 06-21-2013, 10:41 AM
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2002 WJ 
Join Date: May 2013
Location: Corvallis
Posts: 1
Wj vacuum line

Had the same issue on my 4.0 ended up just bring the vacuum lines for my idle speed controller. Had one totally disconnected and another all cracked and dried. Needless to say, those $2 parts fixed the idle problem, and overall performance.
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