Jag XJ12, 1994, 100K, 6.0L V12.
I just fixed the Tach and now it seems to indicate the rpm's are too high. At 70mph it indicates 4000rpm. Transmission shifts OK, the tach needle drops a bit at the shifts. Idle is around 2000rpm in gear (indicated) and it won't lower when I turn the air ajustment screw in. I recently disconnected the neg battery terminal to try and reset the system. Car starts and runs great, just can't bring the idle down.
Thanks for any help!