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General Forums => The Mess Hall => Topic started by: bukdwn on September 13, 2011, 11:19:05 PM
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OK. let me see if i can ex plane this correctly! So i removed the old 2.5L Throttle body and removed both the AIS and the TPS. Both are new. I fully cleaned up the junk yard fined 4.0L TB. When i removed the AIS motor, i only removed the motor not the housing that it bolts to. The housing has (4) small security type star bolts and i did not remove that from the 4.0L. From looking at both housings, i could not really tell any difference between the two. When i went to install the new 4.0L onto the manifold ,the AIS motor housing has a small de-tent (Sorry for the spelling) witch must be for alignment reasons. So i got the dremal out and removed it . The throttle body fit just fine after that! I re-installed everything and started it up. The normal high idle when replacing the AIS motor but would not come down. Turned of the engine and thought it must be trying to relearn it self. Turned on and off the engine a couple of times and the idle came down to normal. The jeep runs great, good mid range. and pulls hills much easier. The problem is when i start the engine when it is cold, the RPM's stay up around 2000 for about 6 seconds and then it will come down to normal idle. Do you think this will be fine or should i swap out the AIS motor housings?
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The housing needs to be moved too, if you notice it has 2.5 on it... or something similar.
Use a standard torx driver to remove, just use a small punch and tap sideways in the little pins in the hole and they snap out.
Dave
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Worthwhile if you grind out the intake manifold to match the diameter of the "new" TB. Forget what the diameter is pre-grind on the 4banger -- its like 52mm or something.
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They make tamper proof torx bits for those also but the punch should work
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They make tamper proof torx bits for those also but the punch should work
yeah, it's like $10 for the set and you get about 20 or so tamper proof bits.
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From looking at both housings, i could not really tell any difference between the two. Could you explane what makes the difference between the two? Has anybody tried this before and found that the 4.0L AIS housing works better besides the high idle start? Buy the way, for the people that are on the fence about this mod. You will not regret installing the 4.0L TB on your 2.5 liter. There is a hill leaving my town about 1 mile up hill and about 15-20% grade may be more in some areas . I use to be able to get to the top in 4th gear but 38 MPH tops. Now 45 MPH in 4th gear. A lot easier to cruz down the freeway also. Thanks guy's for the info!
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From looking at both housings, i could not really tell any difference between the two. Could you explane what makes the difference between the two? Has anybody tried this before and found that the 4.0L AIS housing works better besides the high idle start? Buy the way, for the people that are on the fence about this mod. You will not regret installing the 4.0L TB on your 2.5 liter. There is a hill leaving my town about 1 mile up hill and about 15-20% grade may be more in some areas . I use to be able to get to the top in 4th gear but 38 MPH tops. Now 45 MPH in 4th gear. A lot easier to cruz down the freeway also. Thanks guy's for the info!
they are different - yes people have tried this before and it doesn't work. they are different size as they are for different engine displacements, the matter is related to air at idle and how much air this IAC (idle air control) valve is letting in, has nothing to do with your speed in 4th gear or anything other than maybe your throttle being opened 1/3 or less. you'll be lacking engine brake and also your revs will come down slower not to mention mpg will also be affected (not by much but it will). other than that they look the same.
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IIRC, the plunger is larger on the 4.0L. I've heard some people keeping the 4.0L plunger but I've never seen it done in person.
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From looking at both housings, i could not really tell any difference between the two.
Look inside, the difference is the size of the hole in the housing and the size of the tip on the IAC plunger that allows air through to determine idle speed. Use the 2.5L IAC housing and plunger.
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The 2.5 needs about 1/2 the volume of air at idle as the 4.0.
It also affects the off idle transition, the valve seems to act like its
helping balance the transition form no throttle to just opening.
I fiddled around swapping housings trying to figure out if I could
make a idle up solenoid for keeping the alternator up..
Dave
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you'll be lacking engine brake and also your revs will come down slower not to mention mpg will also be affected (not by much but it will).
OK, so i did the swap. Changed out the housing, installing the 2.5 into the 4.0L . Also ground out the intake manifold to match the diameter of the "new" TB. This is what i think. Knowing that the modifications might take a few starts and miles to re-learn it's self. I think it had a little more pull with the 4.0 housing on it. Call me crazy, but i think it had a little more spunk! I know i need a new air intake to get more air. i still have the stock air box with the mods found on this site. I'm going to drive over into the bay area tomorrow, so i will wait till then to make my decision if I'm going to re-install the 4.0L housing back on. As far as what SHARPXMAN said about the lack of engine braking and the engine RPM's coming down slower! I did not find that to be the case. The only thing was the cold start, high (2000 rpm) idle for a short 6 to 10 seconds then it would go down to normal idle. I also noticed when at idle, it seems a little higher than normal, I could not tell buy the RPM gauge if it was higher. What do you guy's think?
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This is what i think. Knowing that the modifications might take a few starts and miles to re-learn it's self. I think it had a little more pull with the 4.0 housing on it. Call me crazy, but i think it had a little more spunk!
since you have a 4.0 and not a bored out (so it's tapered on the bottom, if you'd like i can explain more) theoretically it's possible but nothing that you'd be able to notice on your own. the only thing that would tell you for sure would be a flowmeter, i doubt the result would be of any relevance.
if you say it comes down in revs the same as with the 2.5 housing then you might have something else going on there, maybe your butterfly is not coming down completely or gets stuck or your throttle cable is not moving freely. If you feel it is running better with the 4.0 housing throw it back on there, will not harm your engine or anything like that.
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The difference on mine was night and day,,, but,,, I have a balance blueprinted, built engine.
I ended up running the 2.5 TB until the 4.0 TB arrived when I installed the 4.0 tb it really woke
up the enigne.. I also have tri-Y headers, a metal
matrix cat and a spintech muffler so the difference in the top end especially is huge.
Dave
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I had the same problem with high idle. I swapped and swapped and then finally swapped out the housing for the sensor as well and it went to normal. I think there might be like a quarter inch difference between the housings but it is enough to really make it sound bad. Just don't break the gasket for the housing. I found my 4.0 at the salvage yard for 15.00, installed it and was happy and leter pulled the intake manifold when doing the head gasket and opened it up as well and was more happy. Verry peppy little engine!
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Nicks92jeeper, What housing did you end up with, 2.5 or the 4.0? This morning i started it up, normal 1800rpm cold start. Came right down to normal idle in about 19 seconds. So i brought up the idle and when coming down from the RPM's it would take a little bit ( about 3 seconds) before it would come down to normal idle. I removed the + and the - from the battery and let them sit for awhile and re-connected them. Started the jeep and the same thing, It takes about 2 seconds to come all the way down to normal idle. I believe the butter fly is not hanging up. Cleaned the TB completely before the install. Also cleaned the motor housing. I thought maybe a air leak? Sprayed Carb cleaner around the TB and motor housing, Nothing changed! Yes, i could just change things around but was hoping someone had the same problem, and had a fix. Trial and error is best but wanted to see what i can find out first! Thanks for all the info!
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I believe that I used the 2.5 housing. I tried the 4.0 but my rpms were at about 4500 rpm and I though that was a bit dangerous. So I used the 4.0 throttle body with the 2.5 sensors and AIS housing. This was last year that I did this mod and my brain is shot right now. I would basically say try the 2.5 housing with the 2.5 sensors. If that doesn't work then try the 4.0 housing. Make sure that you have a good seal as well so no intake leak.
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Found a picture and I took everything off the 2.5 and put it on the 4.0. This picture also shows how much you will gain if port math or whatever with the intake manifold to match the TB. It would be a noticeable difference in my opinion. The 2.5 is on the left and the 4.0 is on the right. the second picture shows a faint line of the potential size it could open up to. the third is opened up. I used a drum sanding bit in my drill press and it made fast work since the intake was out.
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Found a picture and I took everything off the 2.5 and put it on the 4.0. This picture also shows how much you will gain if port math or whatever with the intake manifold to match the TB. It would be a noticeable difference in my opinion. The 2.5 is on the left and the 4.0 is on the right. the second picture shows a faint line of the potential size it could open up to. the third is opened up. I used a drum sanding bit in my drill press and it made fast work since the intake was out.
that's not a 4.0 on the right btw, it's a bored out 4.0, the stock one tapers on the bottom (similar to the 2.5 but larger diameter) - the machining job is not that great but at least whoever did it stopped before the butterfly to prevent getting it out of spec when the throttle is closed - you got a bored out t/b to 60mm for $15 which is a really good deal.
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Actually I bored it out with the drum sander on a drill press and just wanted to get it good enough. You gunna make me cry! I bored it out a bit on both ends and after this picture I smoothed out the sides so they were smoot and consistant. I like the fact that you noticed though!
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Actually I bored it out with the drum sander on a drill press and just wanted to get it good enough. You gunna make me cry! I bored it out a bit on both ends and after this picture I smoothed out the sides so they were smoot and consistant. I like the fact that you noticed though!
that's actually a pretty decent job for first time and on a drill press
reason i notices is b/c i made a few myself :lol: bored out to 64mm
turned out like this (last ones i made, i busted a few trying to get largest bore but neve been able to go past 64mm)
(http://i57.photobucket.com/albums/g222/sharpxmen/Misc/64mm_TJ_YJ_throttleBodies.jpg)
(http://i57.photobucket.com/albums/g222/sharpxmen/Misc/64mm_TJ_YJ_throttleBodies_2.jpg)
(http://i57.photobucket.com/albums/g222/sharpxmen/Misc/64mm_TJ_YJ_throttleBodies_3.jpg)
(not trying to sell them, have none at the moment - just in case someone will think i'm pimping them out)
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Here's what i ended up doing. I removed the 2.5L housing and re-installed the 4.0L housing. The 2.5L housing on the 4.0L TB did not idle the best. The idle would take a little longer to come down to normal idle. Everything in this jeep has been changed as far as a full tune up. The engine runs like a top! At cold start up, the TB with the 2.5 housing would be around 17 to 1800 RPM's. With the 4.0 TB housing installed the cold start is around 18- 1900 RPM's. I need to install a new air filter system, i can tell with the stock air box top unclipped for straight threw air, that it comes up in rpm's a little faster. So, if your having problems with your idle with this mod, try installing the 4.0L housing! Thanks for all the info and the fact's forum! i really appreciate it.
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how's your air filter? also, do you have lot of blow-by?
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SHARPXMAN, As far as the air filter, I have the stock air box and filter. The filter has been changed in the last 300 miles. forgive me but i'm having a brain fart! What exactly do you mean buy blow buy?
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Blowby is the gases coming from the crank case. (Usually from around the rings)
If the crankcase vent is plugged (Small brass fitting on valve cover) it will blow a
lot of vapor where it does not belong. Which will gum up the IAC and the passage it sucks through.
Dave
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Blowby is the gases coming from the crank case. (Usually from around the rings)
If the crankcase vent is plugged (Small brass fitting on valve cover) it will blow a
lot of vapor where it does not belong. Which will gum up the IAC and the passage it sucks through.
Dave
correct, will also mess with your idle that's why i asked (and that's regardless if the small vent is plugged or not, too much and will blow thru both).
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When I did the head gasket I examined everything to see if there was any blockage and the vents in the valve cover was completely clogged so I opened them up again. The reason I looked was the air filter was coated in oil so I knew something was clogged up but I didn't notice anything on the idle as I did a lot of mods at this time.
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@ Sharpxmen. Those are some real pretty Throttle bodies! You did a very good job on boring them out.
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Your high idle at startup sounds like it has nothing to do with the IAC, but more likely a vacuum leak. It comes down as the IAC adjusts for the vacuum leak in an attempt to correct the high idle.
Really, you should prolly run the 2.5L IAC housing and plunger.