I had idling problems and followed the replies to my earlier post, now when I first start up my idle is about 850 rpms, after about 90 seconds it revs up to over 2000rpm! After about 4 or 5 minutes it comes back down somewhat but kind of a pain waiting for it to settle. I have a new control valve for the idle screw adjustment but theres no difference in it and the old one.


1989 XJS V12 FI 5.13


Any help appreciated.


DickC

 

Sounds like you've replaced the AAV-Aux Air Valve. That's a common culprit.

But, since that didn't help....


There are various 'could be' possibilities. I'd be tempted to begin with fundamentals: 1) throttle blades both gapped at .002" 2) both throttle bodies clean 3) throttle linkage synchronized 4) throttle bushings in good shape (the bushings at the bellcranks at the rear of each inlet manifold).

After that ...or before, doesn't matter....start looking for any and all air leaks. Don't forget the check the bolts that hold the air cleaner rear housings onto the throttle bodies.

Others will chime in with more.

Cheers
DD

 

Thanks Doug, will do as you say.
Dick C.