Topic: throttle body upgrade?

[FourbangerYJ]

do you have to change sensors with a throttle body for a tj?

The sensors from your 2.5L go on to the bigger TB.

[aka-justin]

You have to swap the AIS and the throttle position sensor from your 2.5 throttle body to the 4.0 thorttle body.  The only difference between the YJ and the TJ is the Map sensor port.

Here's one of the many articles with more details about the swap.
http://www.4x4wire.com/jeep/tech/engine/throttlebody01/

[Jeffy]

do you have to change sensors with a throttle body for a tj?

Yes, at minimum the IAS needs to be swapped as well as the housing otherwise you'll get an internal vacuum leak and a high idle.

[cletz97]

what if i don't have the sensors for the 4.0 throttle body?

[Bounty Hunter]

"what if i don't have the sensors for the 4.0 throttle body? "

You don't need them, use all 2.5 stuff on the TB.

[st.chevrolet]

You have to swap the AIS and the throttle position sensor from your 2.5 throttle body to the 4.0 throttle body.  The only difference between the YJ and the TJ is the Map sensor port.

Here's one of the many articles with more details about the swap.
http://www.4x4wire.com/jeep/tech/engine/throttlebody01/

[cletz97]

ohhh alright haha
now i jsut feel dumb

[cletz97]

the two AIS sensors on my throttle bodies are the same could i keep the one form the 4.0 on and use it? or do i have to still hange the houseing, i didnt before and its has a really high idle, so i guess today ill try using the sensor from the 4.0 instead of the 2.5 and see how that works out.
just has anyone else tried this?
mine both look like the one on the right (sensor plug in part)

[jfrabat]

the two AIS sensors on my throttle bodies are the same could i keep the one form the 4.0 on and use it? or do i have to still hange the houseing, i didnt before and its has a really high idle, so i guess today ill try using the sensor from the 4.0 instead of the 2.5 and see how that works out.
just has anyone else tried this?
mine both look like the one on the right (sensor plug in part)

Regarding the high idel, something you may want to check is the small hex screw that screws up from UNDER the TB that restricts the plate closed position; if set wrong, it can leave the plate open, causing a rough idle (I had this problem, and it was driving me NUTS).  Now, as far as the sensors, I would jut go ahead and use the 2.5L and avoid problems...

[bjohn8758]

I'll tell you this much.... I put on a 62.5mm bored TB + a spacer and it did make a pretty big diiference in mid-range power. However. if you don't massage the exhaust (AIR IN AIR OUT) you won't notice it much..... I plan on working on the exhaust soon,

BTW....any ideas on flow??


"94 YJ
2.5
AX5
No other mods

[jfrabat]

BTW....any ideas on flow??

If you want to go all out, headers, high flow cat and cat back system is the way to go; but that can ge expensive.  I left the stock headers, and used a gibson cat back for some time, then my cat blew up.  I am now installing a Carsound by Magnaflow high flow cat and borla Stailess Steen cat back (all the crap from the cat ended up in my gibson muffler).

[alfajeep]

Ive noticed that after switching over to the 4.0TB, it takes longer to crank on cold starts.  Has anyone else had this problem?  I have reset the ECU after install, and its been 300 mi after the swap, going to try to go back to the 2.5 and see what happens.

[jfrabat]

Ive noticed that after switching over to the 4.0TB, it takes longer to crank on cold starts.  Has anyone else had this problem?  I have reset the ECU after install, and its been 300 mi after the swap, going to try to go back to the 2.5 and see what happens.

IIRC, it takes 50 warm-up cycles for the ECU to "learn"...