• Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

installed a 62mm throttle body

1

1993 Red XJ

NAXJA Forum User
Location
Flora, IL
Just installed a BBK new 62mm throttle body and now my idle is at 8-900 RPM. Should be at 500 RPM. It's not the set screw I have already tried that. I had 500 RPM idle on the stock throttle body. Is the computer trying to get used to the new throttle body or is it defective. It does drop to 500 RPM when it is put into gear.
 
Sounds like the IAC valve might be going bad. Also, did you replace the throttle body gasket when you did the swap?
 
If you did not re-boot the computer, I would suspect that it is not yet used to the new throttle body. The symptoms of a faulty IAC are usually an unsteady idle, or surging while decelerating.
 
I did disconnect the ground on the battery for 30 minutes and did the headlight turn on and turn off procedure. Yes it came with a new gasket and it was way better than the stock one that was on there. I don't think its the IAC. It's consistently around those RPM when warm or cold.
 
I reinstalled the stock throttle body and my idle returned where it is supposed to be. Has anyone else had issues when installing a bigger throttle body?
 
I installed a 60mm TB and had no issues. The PCM will need a number of drive cycles to fully learn a new TB. If you re-boot the PCM, it is running off pre-programmed data for stock parts until it learns.
 
Any odd noises with the 62mm throttle body? A buddy had a BBK 62mm on his for a bit and it whistled a ton at certain throttle inputs. He ended up selling it and having a machinist bore his stock one so it was 60mm all the way through. Unless there was a significant air leak I don't think it would make that much difference. I would drive around for a bit like Tim suggested and see how it is after a week or so.
 
Whistling is easily solved by radiusing the edges of the Idle Air inlet and outlet. Those are the rectangular slots in the side of the bore.


1993 Red XJ said:
I ran it for a week and nothing changed.
Click to expand...

Then I would suspect the IAC stepper.
 
Maybe you have a slight leak in one of the vacuum lines causing a high idle. Like the rubber elbow for the MAP sensor? Maybe it was fine on the old TB but it cracked when you swapped?
 
1993 Red XJ said:
My motor has a bigger cam and has a free flowing exhaust with cold air intake.
Click to expand...

Your stock throttle body will still handle that. Heck, the stock throttle body isn't even a restriction on our race motor.

That being said, that TB has a mechanical adjustment on it. Crank it down just until the idle doesn't drop any more.
 
You must log in or register to reply here.

Similar threads

Jeep70
96 XJ Transmission issues
Replies
3
Views
49
RCP Phx
R
V
High temp woes
2
Replies
21
Views
399
Vitzaa
V
C
Cranking Time
Replies
6
Views
80
CBJeeper
C
C
'98 XJ p0123 help, TPS high voltage
Replies
18
Views
3K
Tim_MN
Tim_MN
A
High pitch whine coming to a stop
Replies
5
Views
3K
chris420
chris420
Back
Top