Hello,
we just purchased a 90 XJS 5.3 for the wife..she loves it..I have a small problem...first, I have good skill with a wrench. but this is driving me nuts...I have flushed the radiator. changed the oil, repaired the tower seal on the rack, brakes and rotors, new tires, thermostats, air cleaners(K&N), tie rods w/ front end alingment, A/C recharge, replaced most rubber lines... OK, here it is. after warm up the engine surges from 750 to 1700 rpms when I put a load on it (AC or drive) it stops and smooths out..also the normal idle is about 1000 rpms...I'm not expecting miracles here but any info would be more than I have now....I cant even find a manual on this car.....thank you in advance...L

 

OK here's what I got so far...I adjusted the linkage to the throttle bodys and it stoped when warmed up. but still does it when cold first thing in the morn...any ideas,.. I also searched the arcives and nothing..thanks ...L

 

this could be the ' AAV ' aka, the auxiliary air valve,

this is mounted on the back of the left hand inlet manifold and diverts air for cold starting , it fails ( sticks ) and then will surge the engine in normal driving conditions, quite tricky to fix, and hard if not impossible to get a new one

as for a manual , you need the Jaguar publications for the XJS , its the original parts manual( part number RTC9900CA isbn-1-855-20400-2), along with the ' repair operation maual '( ROM ) part number AKM3455( isbn 1-85520-262-x) , these can be bought direct from Jaguar, or on the internet

hope this helps

BB

 

Yes sounds like air is getting into the engine from somewhere, it happend to our XJ40 V12.

 

yes,this helps .. I have to pull the intakes anyways to do the cam covers that are leaking and the dist, plugs,wires... I will inspect and clean...I had found a hole in one of the rubber tubes running to the AAV. didn't know what that was...and repaired that about a week ago...thank you very much for the response...want to keep the wife in a safe dependable car...L