Engine Performance problem
1988 Jaguar XJS V12 Two Wheel Drive Automatic 92000 miles
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my 88 xjs V12 idles rough when the engines is hot. i took it to my mechanic and i had all my injectors cleaned out. when they put the car the tunescope they found the left bank cylinders running richer than the right bank. they tried putting a new computer in it but it made no differance. the car runs fine driving but as soon as you stop it idles rough, you can clearly feel the engine miss when you put your hand over the exhaust. i have good oil pressure and the engine isnt smokey. my mechanic (who is a jag speciaist) has no idea any help would be realy apreciated.

Thank you