Topic: 63mm TB bored & ported for 91-04 4.0L & 2.5L

[Guardian7]

This caught my attention today for $89 it might be worth a try. They are boring out core TB's adding a new thottle plate and selling at a good price. On a recent offroad trip I spoke to a guy who told me the best power mod he ever did on his 2.5L was the 4.0L throttle body swap which is only 54mm up from stock 47mm so I'm thinking this 63mm will make a really good power gain.  http://www.xtremefi.com/index.html

[Bounty Hunter]

Is too big a TB ever a bad thing?

[Jeffy]

Is too big a TB ever a bad thing?

It can be.  I know a few people who have had problems with the bored 4.0L's on 2.5Ls.  I believe there they were having bucking problems.  One problem is getting too much air without increasing the fuel which causes the engine to run lean.  Not only is there more air getting into the engine, but because of the increased passage, velocity usually decreases which throws off the MAP.  The MAP thinks there is less air entering then there really is.

[Guardian7]

I also found an Ebay store selling new oem 4.0L TB's for $89 which may be a better choice and no core charge.

http://stores.ebay.com/PROTECHGOTITALL

http://cgi.ebay.com/ebaymotors/THROTTLE-BODY-JEEP-WRANGLER...

[chrisfranklin]

I read the ad and it looks like the same outfit (Texas-based) I ordered with on Ebay.  

I use their 63mm TB and quality of it is fine, especially for the money.  There is core swap and a $50 refund if the core you send them is in good shape. Versus doing a $400 62mm TB sold buy some online rockshops, mine was a reasonable deal at $150 with a follow-up $50 core refund.

I don't really have a frame-of-reference in mind as far as how the 2.5 engine runs when at the proper air/fuel ratio.  I wouldn't be surprised if my 2.5 is, now, running lean in a few spots with the 63mm TB.  MAP adjuster would probably do wonders, but I'd want to adjust it properly for CARB smog testing.  So right now I'm MAP adjuster-less.  

Overall, though I'd say the 63mm TB is a good performance buy; WOT seems much improved and you can torque around town barely opening the throttle now and cruise at low speed in 4th and 5th gear.

[Guardian7]

Chris, did you have any problems with the larger TB unit?

[chrisfranklin]

No real problems, Guardian.  But the $100 you put in to the 63mm job may have to be supplemented with another $130 + time you put in to buying/installing an adjustable MAP sensor.  If your TJ is a street ride, then you may be, too, looking at emissions testing issues in Ca.  which can run up a bill all there own to get fixed.

I'm probably going to take a roadtrip down to Turbo City in Orange, Ca. to get an adjuster installed and get everything properly emissions tuned.

[Guardian7]

The guy I met on my recent offroad trip told me his 97 TJ passed smog after doing the 4.0L TB swap which got me even more interested.
Jeffy also mentioned it may run leaner which could even help to pass the smog test.

[Jeffy]

The guy I met on my recent offroad trip told me his 97 TJ passed smog after doing the 4.0L TB swap which got me even more interested.
Jeffy also mentioned it may run leaner which could even help to pass the smog test.

I've passed SMOG twice with my Stock 4.0L TB.  The Visual isn't really the problem though.  If it causes the CEL to get triggered that's bad news.  My engine only has 60K miles on it and I've owned it since new.  If your engine is already borderline a bored 4.0L might push it either way.

[chrisfranklin]

For the price it's a good move - I've had it almost a year with no problems.  So, you should probably order one up.  You'll probably get it and not have any problems.

One thing you might encounter, emissions-wise, with the higher airflow is an increase in NOX readings (apparently a product of a lean running condition; jeep sets the air/fuel ratio based on intake air temp and manifold air pressure, not mass air flow). The only reason I am saying this is because I encountered some NOX-test CARB problems, myself, after intake mods (but prior to my own 63mm install).  If you are testing ok with CARB now, and you order the 63mm,  you  might want to keep the old 2.5 TB just in case.    :D

[Bounty Hunter]

another $130 + time you put in to buying/installing an adjustable MAP sensor.

$15-$20 to build one yourself with Radio Shack parts.  Easy writeups on the web.

[chrisfranklin]

That sounds good for the money. But, I don't have a long track record with doing successful radio shack-built jobs.  Knowing me, I'd blow $1000 worth of work time trying to save $100  

[dledle 16]

I can't use my 62 tb because of the poor mixture, and installing an adjustable MAP sensor is probably the solution.

Where can i find it ?

Thank :idea:  :idea:  :idea:

[SKI BOY]

HEY GUARDIAN,

 FYI- THAT E-BAY SELLER "PROTECHGOTITALL" IS NOT SELLING OEM 4.0 TB'S!! THEIR LISTING READS AS THOUGH IT IS A 4.0L BUT IS ONLY A 2.5L AND IS NOT AN OEM PART. I BOUGHT ONE A FEW WEEKS AGO AND THEN HAD TO DEBATE WITH THEM TO DO A REFUND BECAUSE THEY DO NOT HAVE THE 4.0L. THE TB HAS THE SIZE THAT IS NORMALLY STAMPED ON THE SIDE GROUND OFF TO HIDE THE FACT. THEY SAID THEY WOULD CHANGE THEIR LISTING BUT HAVE NOT TO DATE. BUYER BEWARE!!!

[Guardian7]

Wow, thanks for sharing that, I think I did see another dealer selling the stock 4.0L throttle body on Ebay and it did look different too. The unit I had posted a pic of was from a company called Extremefi but they may be doing the same thing that you discovered.