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Ronnie, ASE Certified Technician
Category: Jaguar
Satisfied Customers: 35857
Experience:  34 years as an Automotive tech
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I have a 1990 Jaguar XJS. The distributor has been changed

Customer Question

I have a 1990 Jaguar XJS. The distributor has been changed from the Marelli to the Lucas. I've changed plugs (0.025), rotor, ignition wires. Car runs well EXCEPT when it is warm idling. I've checked the AAV and it expands when tested in warm water.
When cold, the car idles fine except a bit rough (shaky). As it warms, it's necessary to put it in neutral at a red light so that it will not idle really rough or even stall. When warm, in neutral, it runs at approx 900 rpms. In gear it will fall below 500 rpms. Ignition has been converted to a Fireball XR700. The throttle bodies seem clean and tight although one of the plastic throttle bushings is cracked. There seems to be a temp sensor on front of right bank that's disconnected.
Would love this motor to run well at warm adle since this appears to be the only problem at this point.
Submitted: 1 year ago.
Category: Jaguar
Expert:  Ronnie replied 1 year ago.

Hello, my name is ***** ***** I am a professional here at Just Answer. I have noticed that your question was not getting a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.

Rough idle can be cause by a few things, one common cause can be an engine vacuum leak so I would start with checking in and around the intake area for any signs of a leak. If its leaking this can also cause the RPM to raise as well. Take some carb cleaner and carefully spray short burst in and around the intake area and see if there is any change in the RPM. If so that would indicate you have a leak. I would also scan the computer system and see if there any fault codes setting. Check this for me and post back with the results and we can work from there.