I own am '88 XJSC with just under 49,000 miles on it. Up until now the car has idled smoothly whether the engine was hot, or cold. Now it has an intermittent issue with an idle that pulsates from just about to die up to 800RPM and back. This has only occurred when the engine is hot and I can clear it by revving the engine slightly about 1100RPM a few times. Everything is fine from then on out. The car still averages 13MPG combined driving and just under 17 at 70-75MPH. This doesn't occur all of the time, but often enough to concern me. I do take rather long trips each summer and most of my driving is in rural areas where folks have never seen a Jaguar much less repaired one. Any ideas as to where I can start looking would be appreciated.

Steve

Submitted by jgilles44@sbcg… on Tue, 07/06/2010 - 23:09

I have a very similar problem with an 89 XJS V12 5.3L. After a short trip of 30 min., once i turn the car off and restart, i get a very low idle and the car will keep dyeing out. I must drive with 2 feet to keep the car running. I notice the oil pressure very low also. None of this happens if I start cold and do not restart after a short trip. 1 or 2 hour trips restart and run fine. Figure that one? I'm very interested in what you find out also.

Submitted by leftlanesi@yahoo.com on Sat, 05/01/2010 - 15:55

My 1990 XJS with 30,000 miles on it does the same thing upon re-starting the engine when it's at operating temperature. Of course, it never does it when I take it to the mechanic. When I start the car after driving a bit, I sometimes have to actually have my foot lightly on the accellerator pedal to keep it running because the low end of the pulsing is sometimes too low and the engine dies. This clears up after about 20 seconds and the engine smooths out and idles fine.

I don't know the procedure for adjusting a throttle bodies or linkages, but I know my air cleaners and new. I will look in my shop manual to see if it explains the procedure. I am looking forward to hearing what you did and if it worked to resolve your issue.

-Kent

Submitted by SE98-32482CJ on Thu, 04/15/2010 - 07:03

Steve you said it idled smoothe hot or cold but now you have a idle problem when hot--right? If cold I would suspect the extra air valve (and check it anyway) but the pulsing idle hot is very typical of out of adjustment throttle bodies and linkage. Follow your manual and check the clearance of each body--also take a good look at your air filters. Let us know.