4.0L Throttle Body Swap Onto 2.5L with pictures and Questions - JeepForum.com
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post #1 of 3 Old 04-02-2013, 05:03 PM Thread Starter
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1995 YJ Wrangler 
Join Date: Aug 2011
Location: Arlington
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4.0L Throttle Body Swap Onto 2.5L with pictures and Questions

Hey guys. While my jeep is in pieces for the alternator upgrade I am doing I decided to swap the 4.0L throttle body onto my 4 banger. Here is what I have so far and I need some advice to finish.

I started by removing everything from the 4.0L throttle body and cleaning it thoroughly. I then removed the 2.5L Throttle body, it seems the previous owner has a spacer on already that I had not noticed. See it below.


You can also see that there is a good amount of oil inside the manifold. Is that a major concern?
Also should I leave the spacer on and just ad the 4.0L Throttle body?
Here you can see the differences in the two TB's.




In the above picture you can note the difference in size. I have swapped all the components off the 2.5L onto the 4.0L throttle body to avoid the idling issues. I also read in JP magazine's May issue that a guy who did the same swap and ran into a high idle at 1100 rpm. Be sure to check the grub screw under where the throttle cable connects. Once I figure out if and how to remove the current TB spacer on now I plan to put the newly built 4.0L back on. Ill take pictures as I go in case I have questions but so far the only problem I had with BOTH TB's were the dang screws that held the TPS on, of course they are torx and i think they used locktight on them. I filed them down so I could grab them with a pair of channel locks, but they were tough so use patience. Let me know what you think about the oil and TB spacer on there.

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post #2 of 3 Old 04-02-2013, 11:30 PM
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1991 YJ Wrangler 
Join Date: Jul 2012
Location: Modesto
Posts: 325
My guess is your CCV is (or was) puking oil into your intake and it's getting into the manifold.
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post #3 of 3 Old 04-03-2013, 11:03 AM
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1989 YJ Wrangler 
Join Date: Apr 2008
Location: Detroit
Posts: 24,680
You probably want to check the PCV and the CCV on the valve cover, Check the hoes to make sure it isn't plugged on both sides and last but not least the PO might not have been the best at changing oil it might be worth your time to pull the valve cover and just give it the once over. There have been more then a few engines with crud built up because the PCV and CCV were not venting correctly.

Please document the swap. Are you going to bore out the intake for the larger throttlebody? The IAC should be checked and cleaned while you have it apart and I think you need to use the 2.5L IAC on the new throttlebody.
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