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-   -   2.5 to 4.0 Throttle body swap. Help!! (http://www.wranglerforum.com/f218/2-5-to-4-0-throttle-body-swap-help-146533.html)

Toms94YJ 03-15-2012 10:09 AM

2.5 to 4.0 Throttle body swap. Help!!
 
Ok, so I have a 4 banger that I am trying to squeeze a little more power out of it. I installed a cold air intake, I just installed 19 lb injectors all good. I picked up a used 4.0 throttle body out of a junkyard yesterday. Installed this morning. After install, I crank her up and the engine goes wide open. I shut it down. Try again, same thing. Everything hooked back up just like with the original. Does anybody have any ideas? Need help here.
Thanks

97wrangler-242 03-15-2012 10:16 AM

Check your iac valve, it needs adjusting. Also, those 19lb injectors won't do any good unless you have the computer reflashed. With those larger injectors the computer is just going to shorten the pulse width and your engine is getting the same amount of fuel

Toms94YJ 03-15-2012 10:40 AM

Sorry to sound stupid, but what and where is the iac valve?
Thanks

gunslinger24 03-15-2012 01:39 PM

I have your answer. There is a small tab on the bottom of your new throttle body that needs to be ground off.

Same thing happened to me!

blazerone22 03-15-2012 04:03 PM

Did you swap out your sensors from the 2.5 throttle body? thats all I did on mine and it works fine... Also you might want to check your clamp holding on your air intake, I pivoted mine around to make it easier to get to but it did catch my throttle linkage... kinda freaked me out until I figured it out...

Toms94YJ 03-15-2012 04:22 PM

Figured it out. You do have swap the sensors. Done and running like a scalded turtle now. Thanks for the help.

SandyMushYJ 03-15-2012 04:57 PM

Lol, scalded turtle. Is there an improvement, then?

Toms94YJ 03-15-2012 05:03 PM

I may have spoke to soon. Ran fine, improved power. But got home, went back out to get some gas and now sputtering, backfiring. Did not want to start back up at the gas station. Made it home. Now there is all kinds of oil in my air intake. Any more ideas?

Xpress 03-15-2012 06:54 PM

Did you hook up the vacuum lines properly? That's blow-by, meaning your vacuum system isn't de-pressurizing the crank.

Toms94YJ 03-15-2012 07:29 PM

Not sure. Everything looks like it is hooked up. I will have to check again tomorrow.

DirtyRob 03-15-2012 08:58 PM

Scalded turtle.......:rofl:
I think I found a new nickname for my YJ :rofl:
I can't hardly stop laughing about that one....that is funny right there

It sounds like you are getting too much vacuum to the throttle body. Check and re-check your vacuum lines Especially the one coming from the valve cover

tim2 03-16-2012 02:03 AM

What kind of improvement will changing to a 4.0 throttle body give my lil 2.5 motor? I have seen this in posts before but am unsure of what this mod actually helps.

Xpress 03-16-2012 01:34 PM

It helps improve acceleration, but the TB itself won't actually improve HP figures- you might see as much as 1hp gains. You really do need to open up EVERYTHING up and down river in order to see significant HP gains. With a high flow intake, a 4.0 TB, bored out intake header to match, borla exhaust headers and a custom exhaust you're going to see probably about 6-7hp in gains. It's enough to make a little difference but you need to do other stuff to see gains.

Toms94YJ 03-16-2012 02:48 PM

Checked the vacuum lines. No leaks. I did install 19lb injectors a couple of days before. No issues. I swapped back the old throttle body. No more oil but still a very rough idle and sputtering/backfiring while driving. Do you have to adjust the timing at all with the19lb injectors. Also taking a while to start up. I have to give it some gas before she will start. Help please.

Xpress 03-16-2012 05:50 PM

Reset the ECM. Also consider doing a full tuneup. People would be amazed at how much can go wrong with these that causes these idle issues.

Toms94YJ 03-16-2012 06:14 PM

How do I reset the ICM? Thanks for the help by the way.

Xpress 03-16-2012 09:15 PM

Remove the positive lead off the battery then ground it to the negative lead for 30 seconds. It will take a bit of time for the ECM to get to know the settings again.

Toms94YJ 03-16-2012 10:30 PM

Thanks. I will try it in the morning. I am also going to check the injectors and see if I have a leak. There is a strong gas smell under the hood. I appreciate the help.

Toms94YJ 03-19-2012 07:43 PM

Leaky injector! Problem resolved. Thanks for the help.

blazerone22 03-19-2012 11:30 PM

So did the injectors with the throttle body help out? I;ve done the TB and have been shopping for injectors...

morvayryan 06-05-2012 09:35 PM

I'm thinking about doing this to my 2.5l but I have a question. (dont mean to thread jack...sorry) i was wondering if after the swap, do you need a new intake rather than the stock 2.5l? If I was to buy a cai do I buy one for a 2.5l or 4.0l?

Toms94YJ 06-05-2012 10:11 PM

I have a CAI on mine, originally bought it for the 2.5, the throttle body is exactly the same in the O.D. It is just bored out more internally so no fit problem. You just need to swap your sensors over from the 2.5 to the 4.0 you will need a security ROTC bit to do it though.

morvayryan 06-05-2012 10:40 PM

Quote:

Originally Posted by Toms94YJ
I have a CAI on mine, originally bought it for the 2.5, the throttle body is exactly the same in the O.D. It is just bored out more internally so no fit problem. You just need to swap your sensors over from the 2.5 to the 4.0 you will need a security ROTC bit to do it though.

Sounds good, thank you!

Toms94YJ 06-06-2012 08:05 AM

Sorry a security torx bit.

jeep30 06-11-2012 08:13 PM

Good info on here.

morvayryan 06-15-2012 05:22 PM

How did y'all bore out the hole on the intake with out getting metal shavings in it?

morvayryan 06-15-2012 08:03 PM

Never mind, I just put a paper towel in it and some painters tape, sticky side up, and bore out the hole a little and the tape caught all the shavings

jonothehut 03-03-2013 05:39 PM

Quote:

Originally Posted by Xpress
Remove the positive lead off the battery then ground it to the negative lead for 30 seconds. It will take a bit of time for the ECM to get to know the settings again.

I am having the same issue as Toms94YJ.
I swapped both sensors. And reset ECM and engine goes wide open. Sits around 5500 rpm. Any ideas?

CarolinaBound 03-03-2013 05:47 PM

All this work for ~1 extra HP. :confused:

Sandstorm95 03-03-2013 07:03 PM

i had the same issue but its because i didnt swap out the iac. if u compare the 4.0 one to he 2.5 there is a huge difference. The 2.5 one also says "2.5" on it to help a little


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