87,88,89 and 90 xjs all had the Renix operating system they have a weak sensor ground system it is VERY important to clean every ground under the hood ,and check them with an ohm meter. Many people will start replacing sensors and other stuff and not ,or will not believe that the wiring harness might need work. It is a known fact that the grounds on these Jeeps are a problem ,the factory knew it back then.