2.5l to 4.0l throttle body swap ??

[insufficient funds]

So I picked up a 4.0l Tb from a 91 cherokee today. I have a 2.5l throttle body spacer on my 95 2.5l Wrangler. My question is should I keep the 2.5l spacer and put the 4.0l tb on top of it or would that just restrict it? Should I just toss the 2.5l Tb spacer?

 

[JPNinPA]

Honestly the spacer does nothing for fuel injected engines except make them whistle. Second the reason you going the 4.0 TB is for more air and less restriction, correct? If you place a smaller opening below the base of the wider TB opening your defeating the purpose of the larger TB. So besides the TB measure the intake opening the TB sits on.
What benifite are you expecting from the different TB?

 

[insufficient funds]

That's what I figured. I got the 4.0 for free off of my buddies doner cherokee. I seen a few guys on this fourm talk about how it gives the little 4 bangger alittle better throttle response. I don't expect better mpgs or for it to do wheel stands.lol

 

[JPNinPA]

If you do it read up on other things to look at like using the 2.5 TPS and iac.

 

[Bounty__Hunter]

The 4.0L TB will not improve throttle response but you will get a little more power and better mileage if you can keep your foot out of it. You won't see improved throttle response unless you remove the taper from beneath the throttle plate in either throttle body. Look down inside your throttle body and slowly open the throttle and you will see just how much throttle movement is needed for the throttle plate to clear the taper and allow air to pass.

I manufacture 62mm throttle bodies with a straight bore, the throttle response is lightning fast on the 2.5L and 4.0L engines.

Most throttle body spacers are large enough for a 4.0L throttle body, so don't ditch it unless you're sure it's a bottleneck under the throttle body. I think the helix bore spacers are a scam, I make mine a smooth 62mm straight through. The air is moving too fast for a helix to do any good.

 

[JPNinPA]

The 4.0L TB will not improve throttle response but you will get a little more power and better mileage if you can keep your foot out of it. You won't see improved throttle response unless you remove the taper from beneath the throttle plate in either throttle body. Look down inside your throttle body and slowly open the throttle and you will see just how much throttle movement is needed for the throttle plate to clear the taper and allow air to pass.

I manufacture 62mm throttle bodies with a straight bore, the throttle response is lightning fast on the 2.5L and 4.0L engines.

Most throttle body spacers are large enough for a 4.0L throttle body, so don't ditch it unless you're sure it's a bottleneck under the throttle body. I think the helix bore spacers are a scam, I make mine a smooth 62mm straight through. The air is moving too fast for a helix to do any good.

The 2.5l tb is a 52mm bore and the 4.0 is 60 mm bore. Even with the taper there will be more air flowing quicker with the 4.0 with the same skinny pedal stomp. How does the taper matter when you just picked up 8 mm? Taper or not the intake likely is 52mm.
Keeping your heavy foot off the skinny petal will always be more economical.

Explain how a TB spacer does anything for a fuel injected engine like the 2.5.

 

[JaShar30]

Its actually funny that i came across this post... In the october issue of JP they talk about different power adders for the straight 4 and 6. This is one of the add ons they talk about. There are a lot of things that can be done to affect the motors to give you that little bit of extra grunt...

I also have a the straight 4 cylinder... And i am curious as to the extra power frm it so plz keep us up on how it works...

 

[insufficient funds]

Bolt on the tps will not come out. Going to have to get creative. Keep you posted after the stubborn bolt let's loose.

 

[Bounty__Hunter]

Bolt on the tps will not come out. Going to have to get creative. Keep you posted after the stubborn bolt let's loose.

Pretty common. Back it out 1/8 turn and tighten, then repeat as many times as necessary until the bolt comes out. Usually works for me on TB's.

 

[insufficient funds]

Got the bolt out finally. The bigger throttle body help. not a ton of power but noticeable. one issue I have is when I let off the throttle it takes longer to return to idle.

 

[JPNinPA]

Glad to hear you got it done. Was the intake opening wide enough?

Thought you only wanted better throttle response? You did use your old 2.5 TPS yes?
Pic you want more power you'll need more fuel, air and cubic inches, then you need to open up the exhaust. There is no single change that makes noticeable power improvements.

 

[insufficient funds]

Ya I used the sensors off of my old tb. The issue I have now is when idling and I give it gas then release fast and it slowly comes back down to 700 rpm.

 

[luis]

Ya I used the sensors off of my old tb. The issue I have now is when idling and I give it gas then release fast and it slowly comes back down to 700 rpm.

I had the same issue when i did the swap. I let the computer do its thing on my tj and all went back to normal

 

[insufficient funds]

I unplugged the battery for a few hours last night and didn't make any difference. we will See if it works it out on it's own.

 

[luis]

I unplugged the battery for a few hours last night and didn't make any difference. we will See if it works it out on it's own.

How many miles have u driven on it? Were all the sensors placed back correctly?

 

[insufficient funds]

I drive it very little it's mostly a Wheeler. Maybe a 100 miles a month. I belive both sensors are installed correctly.

 

[JPNinPA]

Give it app 500 mi since you unplugged the battery to relearn settings.

 

[Bounty__Hunter]

I unplugged the battery for a few hours last night and didn't make any difference. we will See if it works it out on it's own.

I generally disconnect the battery and touch the pos/neg battery cables together. Turn the headlight switch on and back off while the two battery cables are touching each other. This will totally reset the computer and it takes 50 key cycles for the computer to fully learn the change made to the engine.

Look down the throttle body with the engine off and have a friend depress the accelerator. Make sure the throttle plate returns to closed quickly. If it doesn't, clean the throttle body and maybe loosen and re-position the throttle plate on the throttle shaft. If it closes quickly, the problem is with the IAC and/or computer.