2.5l to 4.0l Throttle Body swap problem! No idle and Revs goes straight to Redline! - JeepForum.com
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Unread 08-01-2010, 09:32 AM   #1
JTR2008
Registered User
1994 YJ Wrangler 
 
Join Date: Dec 2009
Location: Columbus, OH
Posts: 17
2.5l to 4.0l Throttle Body swap problem! No idle and Revs goes straight to Redline!

So I just swapped out my 2.5L throttle body and put in a 4.0L throttle body. everything went in smooth and everything is on tight, and I used the original sensors but when i turn the key and start the car, the revs just go straight up and doesn't stop and i shut the engine off right away. I checked the the flap and its staying shut. I'm no mechanic and i don't have a clue why it is doing this. Any help would be great.

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Unread 08-01-2010, 09:41 PM   #2
Que89YJ
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1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
Posts: 14,549
You have a vacuum leak. Check all the vacuum lines.
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Unread 09-08-2010, 06:41 AM   #3
YelloJeep
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1991 YJ Wrangler 
 
Join Date: Jan 2010
Location: Simpsonville, SC
Posts: 542
Quote:
Originally Posted by JTR2008 View Post
So I just swapped out my 2.5L throttle body and put in a 4.0L throttle body. everything went in smooth and everything is on tight, and I used the original sensors but when i turn the key and start the car, the revs just go straight up and doesn't stop and i shut the engine off right away. I checked the the flap and its staying shut. I'm no mechanic and i don't have a clue why it is doing this. Any help would be great.
Did you get this straightened out? I also just did this swap and when I started it I held my breath waiting for the RPM's to shoot up (I keep hearing people say that is what happens) but it started right up as if I had done nothing. I did notice that it idles around 900-1000RPMs but I can deal with that. I have noticed a pretty good difference in power (not HUGE..). I see alot more of 5th gear and I think maybe I can now turn some 33's without too much strain... Before I was thinking 33's would just be too much but now I think it can handle it.
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