Right so heres the story...my XJ was idling perfectly until I decided to install my new throttle body which had been bored under the butterfly to 60mm.

Installed the new throttle body, cleared computer memory ( the whole postive lead touching block for at least 30 mins...reconnect to battery, turn key on and turn lights on...)

Immediately idle was high when first started it up...eventually came down.
Waited a few days and cant work out tbe high idle...
** It seems to take 3 seconds for the idle to come back down when youve taken your foot off the gas. You can do 50km hour, take your foot off and she drives like shes in auto pilot.
No issues accelerating, gear changes are smooth.
You can be cruising st 1100 RPM / 30 Mph...tap the gas to rev to 1400rpm...foot off the gas...takes 3 seconds to come back to 1100 again.
First thought was IAC motor....so I changed it (Mopar)...even though it had a new one 1 year ago.
No change.
Did a smoke test....no vacuum leak.
No change....still the same idle up high.
So I changed back to the old TB ....bingo....back to normal....idles perfectly but Ive lost the quick throttle...
So I put the bored one back in....the butterly springs back nice and quick....
O2 sensors have been replaced...NTK ones..

I tested voltage ....all good.
Can it be the TPS or the MAP sensor?
Folks here are saying something is not reading the unmetered air???? If thats the case how do you get it to read the air 100%?

I replaced my TB with a 60mm one and had the same issue after the install with a high idle. Turned out it was the set screw underneath the throttle return spring was out to far. Dialed it back and bingo. That screw sets how much the valve is open during idle. Might be worth a shot to take a look. You have to take the TB back out though. Good Luck

Thanks Ricky, wheres the screw on the TB to adjust the spring?

Underneath the TB in the corner under the throttle return spring. Take off the TB and turn it over you can't miss it. Try backing the screw out a bit. I had to do it like 3 times and ended up pretty much backing it out all the way. Where did you get the new TB from? Just curious

Sounds right. Also, keep in mind if its all the way out, theres the poss that under heavy load and if you just go full pedal off (no pedal press at all) its poss it can stall the motor. So just be careful that when you adjust it out, that you do a hard accel test with sliding the foot off the pedal and instant no pedal and see if it wants to stall. If it does then add back a little open.

Ok Im getting somewhere, its working but it needs a little more but the plate wont go down anymore.
The screw can keep going but the plate wont go down anymore??
I have held the TB up to a light and i can see light coming through gaps in the butterfly plate...is this normal?
I bought my TB off Ebay...I think he goes by happitail?

I would think some small gaps in the butterfly valve are acceptable. Also I wouldn't expect your idle to be exactly the same as with the stock TB since you are now getting more air flow. Mine went up to just shy of 1000 rpm at idle. But it is constant. I actually did the 703 fuel injector upgrade shortly after the new TB and have to say the 2 compliment each other very well

Almost zero gaps as the IAC allows are through. Something with the butterfly is FUBAR.

Try this. Loosen the butterfly screws. Allow the butterfly to set. If you have to move the stop screw, do it. Retighten the screws. Check the stop screw adjustment.

Ok, this has helped significantly.
However my next problem now ( has just started since adjusting this screw) if I rev the truck past 3000rpm it is stuck there.
I have to pull over and place in park when revs drop...truck stops and an agressive shrug.
Ang ideas to stop that?

Take the throttle body off and get the butterfly right. Also get the stop screw set correctly. You should JUST see a little bit of light arounf the butterfly. I think the body and butterfly are binding somewhere.

I had a similar thing happen when I bored out mt TB. take off the TB and remove the butterfly, take some scotch bright pads or sand paper (600-800 gritt) and clean the burrs off the inside of the TB. You should also smooth out the edges of the butterfly and make sure you put some high temp grease on the bearings before you re-assemble it. Make sure the stamped numbers on the butterfly are on the top of the opening when the TPS is in your left hand.
I hope this helps.

Now THERE'S a good answer!!

Thanks.

No problem