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Unread 10-10-2013, 06:00 AM   #1
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2002 TJ Wrangler 
Join Date: Jun 2010
Location: Warren, Michigan
Posts: 477
High idle/rpm

2002 TJ 4.0L
140k Miles
32RH Auto

Hello all, lately my jeep has been acting very funny on me. About a week ago I noticed that after I had driven the jeep (duration didnt matter) and went to park it, as I put it in park, the rpms would shoot up, then slowly go down. It went from doing that all of the time to, now when sitting idle at a light, or just in park, the rpms will gradually rise, then fall, then go back up then down.

What makes this more odd is I noticed that when I go to turn on my heat (for one the heat isn't working properly it is only coming out of the defrost vents) the rpms will go up, and the pressure of the heat when it exits the vents will increase. Then when the rpms drop, so does the heat pressure exiting the vents.

I'm not sure if this is a IAC issue, or TPS issue. I know my throttle plate is clean cause I keep it clean. I'm almost wondering if this has something to do with those vent hoses having a leak? But I'm not sure if that can cause spiratic high rpms or not. Not to mention the heat only coming out of the defrost vents issue occurred the end of last winter. This high rpms didn't occur until a week ago.

Thank you


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catnip15 is offline   Reply With Quote
Unread 10-10-2013, 07:01 AM   #2
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2003 TJ Wrangler 
Join Date: Apr 2010
Location: , MA
Posts: 192
I would remove and clean your IAC valve and TPS sensor(while your in there). At the least, you can eliminate them "being fouled/dirty".
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Unread 11-25-2013, 06:29 PM   #3
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Not sure if you figured this out yet, but it sounds like a vacuum leak to me.
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Unread 11-25-2013, 08:22 PM   #4
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2000 TJ Wrangler 
Join Date: Aug 2005
Location: Colorado
Posts: 15,126
Originally Posted by jeepsrgreat View Post
Not sure if you figured this out yet, but it sounds like a vacuum leak to me.
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Unread 11-25-2013, 08:36 PM   #5
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2003 TJ Wrangler 
Join Date: Jul 2013
Location: Fort Worth, Texas
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I agree with the vacuum leak because of your heater only blowing through the defrost vents. Look under the hood for a disconnected hose. I'd start at the manifold and follow it out from there. I bet that's your issue.
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Unread 11-26-2013, 05:23 AM   #6
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1996 XJ Cherokee 
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There is a vacuum line under your battery into the tub.. look there.. that one is overlooked a lot
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Unread 11-26-2013, 07:52 AM   #7
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Location: Long Island NY
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I had the exact same thing on my 2005. The RPM issue was a vacuum hose popped off so the RPM became higher and all over the place. As for the heat, it turns out that the vacuum hose that came off was the one that controls the heat and defroster controls. I looked around the engine compartment and found a hose off a vacuum port and once I reinstalled it the RPM and the heater controls all came back to normal.
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