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Author Topic: **2.5 to 4.0 Throttle Body question**  (Read 1709 times)

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OH-YJ

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**2.5 to 4.0 Throttle Body question**
« on: June 02, 2009, 03:12:37 PM »
First off, this forum is great. I'm a rookie so I love that this is strictly 4bangers. Anyways, I swapped out the throttle body on my 2.5 for a 4.0 a few days ago and whenever I start her up, she revs to 2500 RPM for a few seconds and then idles down to 1250 RPM. I've tried disconnecting the battery, didn't work. I've also heard from a few places that I need to give it time and the computer will fix this issue. Any help would be greatly appreciated!

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st.chevrolet

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Re: **2.5 to 4.0 Throttle Body question**
« Reply #1 on: June 02, 2009, 03:23:11 PM »
A search would have taken you to this:   http://4bangerjp.com/forums/index.php?topic=8.0
« Last Edit: June 02, 2009, 03:23:40 PM by st.chevrolet »
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Offline Jeffy

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Re: **2.5 to 4.0 Throttle Body question**
« Reply #2 on: June 02, 2009, 03:27:18 PM »
Sounds like a vacuum leak.  I'm going to guess that the AIS housing wasn't swapped but the AIS motor was.  If that's the case then that's your problem.  You need to swap the AIS housing.
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Offline jfrabat

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Re: **2.5 to 4.0 Throttle Body question**
« Reply #3 on: June 02, 2009, 04:56:13 PM »
Also check that the plate on the 4.0TB is closing completely; there is a hex screw on the bottom of the TB that limits the plate, and when I bought mine, it left it a bit open which caused RPM's to shoot up to about the same as yours are...
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OH-YJ

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Re: **2.5 to 4.0 Throttle Body question**
« Reply #4 on: June 04, 2009, 09:07:33 PM »
I swapped the AIS housing and motor over to the 4.0 (the 4.0 didn't have the housing when I bought it). I also checked today to make sure the plate is closing properly and it is. I took everything apart, put it back together, and when I fired her up the first time, all was back to normal, but then I started it again and she revved up like she has been. I have no idea...  :puzzled:
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drunkencityworker

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Re: **2.5 to 4.0 Throttle Body question**
« Reply #5 on: June 04, 2009, 10:59:13 PM »
I may be way off but on mine there was a hose that came out at the base of tb that needed a screw in it. Obvious but just checking
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OH-YJ

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Re: **2.5 to 4.0 Throttle Body question**
« Reply #6 on: June 08, 2009, 06:10:42 PM »
So it was the AIS housing. I swapped that last night and she doesn't rev up too bad (almost 1500 RPM), but she slowly comes down and still has a high idle (around 1050-1100 RPM). Much better than before, is this more of a normal idle for this upgrade? Any way to get it even lower?
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Offline Jeffy

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Re: **2.5 to 4.0 Throttle Body question**
« Reply #7 on: June 08, 2009, 06:12:54 PM »
It should idle at 700-750RPM.  Did you reset your ECU?  If the idle isn't dropping further I'd look for a vacuum leak.  Is that a YJ TB or a TJ TB?
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Offline Bounty Hunter

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Re: **2.5 to 4.0 Throttle Body question**
« Reply #8 on: June 08, 2009, 08:31:45 PM »
I think your best bet is one of my 62mm Performance Throttle Bodies :thumb:
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