Jaguar Repair: rough idle, vacuum ports, jaguar shop

Question
QUESTION: have a 1984 xj6 the head has been replaced along with other things vacuum lines tune up etc. still has variations in idle timink maybe

ANSWER: Hi Anthony,
The Series III XJ-6 is noted for having a rough idle even when everything is good. The rough idle is noted by feel in the car but not noted by any variations in the tach. If you see variations in the tach, then you may have a problem. One of many causes could be ignition timing or a vacuum leak but can be caused by many things.

Was it a Jaguar shop that did the head?

Check all the vacuum ports to see that they put all the hoses on including the one under the center of the intake manifold (hard to get to) Test the amount of vacuum on the vacuum port that enters the fire wall on the lower right side. Install a "T" fitting and measure the amount of vacuum at idle and let me know what it reads.

Do one test by pinching closed the vacuum hose on the distributor to see if it smoothes out any. Recheck the timing. Reset the idle mixture and idle speed.

Note any valve noise.

Howard

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QUESTION: they left off vaccumn line on head as you stated advance timing rotate dist. clockwise   ?

Answer
Yes, On any engine with a vacuum advance unit you can just follow the trail of the vacuum on into the unit and on in around the dist shaft to see the direction the dist shaft rotates. In this case you can see that the dist shaft rotates counter clockwise so to advance the timing you move the dist clockwise. So you are correct. If the car still has a sticker under the hood use those specs as they always override what your manual says.
Howard