2.5L to 4.0L Throttle Body Swap. - JeepForum.com
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post #1 of 5 Old 04-07-2019, 03:13 PM Thread Starter
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2.5L to 4.0L Throttle Body Swap.

Been reading online and in some other forum sites about swapping the Throttle Body on my 95 YJ's 2.5L for the 4.0L Throttle Body for a slight increase in HP.
From my understanding as long as I retrieve the throttle body from a similar year model 4.0 its pretty much plug and play installation. I have also read about people replacing the stock single stream fuel injectors with 4 port fuel injectors for increased fuel atomizing thus giving better fuel mileage and also slightly increased HP and throttle response.

Do you guys think these are worthy mods to look into? I mean, from what I've found online both mods would probably run less than $150 and seem like they could both be finished in an afternoon.

I have also found some 12 port injectors that require an adapter or pigtail for the electrical side of the Injector. Would these make much of a difference over the 4 port as far as performance and MPG?

For the record. I do not plan to bore the Intake Manifold, YET. I do plan on doing this in the future but I just don't have the resources to have this done at the moment.

Any input will be appreciated more than I can express.

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post #2 of 5 Old 04-11-2019, 01:57 PM
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On the 4-hole, both my XJs ran smoother. I did not notice much if any power increase. I do have a set up 12 holes, but not installed. One of the member here (CobraMarty, who I bought them from), said best upgrade he did.
I have bored out my TB on a 4.0L. So to a dia of 60mm. It did give more power. I noticed it in the mountains of WV. I did install a BBK 62mm TB. The motor sounded throatier, sort of V-8. I think the motor ran a bit rougher. I have not run it much since. Might need to reset the EMC. Also, I have an aftermarket header and 2.5 exhaust. You would see gains or more gains as you upgrade both the intake side and exhaust side. You might also, have a bunch of upgrade and see slight gains. Then replace, or bore out the TB and notice a gain. Might not see that, if only the TB upgrade.
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post #3 of 5 Old 04-12-2019, 02:27 PM Thread Starter
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Thank you for your reply. I was planning on buying the TB a couple days ago but I got some bad gas in my Silverado that cost me around $90 to rectify so that set me back a couple days but I got it fixed without having to replace injectors or anything major so I’m thankful for that. Possibly next week on the TB and maybe another week or two on the injectors. I’ve read a lot of different experiences on the upgrades so I’m curious to see how they effect mine. I put some fuel treatment and injector cleaner in it the other day and that actually seemed to help some.
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post #4 of 5 Old 04-14-2019, 07:27 PM
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I’ve had a few yj 2.5s and the Tb swap or injector swap never was really worth the effort. You get a better result from and in depth tune up and regular maintenance IMHO. Plugs, leaking vacume lines, loose exhaust joints. Putting smaller tires on the 2.5 You will be farther ahead saving your hard earned cash and spending it on a 25 year old neglected part.
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post #5 of 5 Old 04-15-2019, 03:30 PM Thread Starter
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I'm definitely planning to go over the exhaust header and pipes with a fine tooth comb. I've got an exhaust leak somewhere that's being pulled back up into the cab when the wind hits just right. I don't have a lot of experience tracing down vacuum lines but I hear carburetor cleaner can be incredibly helpful with that.

I haven't pulled them and looked but I'm pretty positive the plugs and plug wires need to be replaced and I'm sure a new air filter wouldn't hurt either.

I've heard of people having oil in their air filters when they change them. What would be the cause of this and how could it be corrected?
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