I am a proud new owner of a 91 xj6. The issue I have is that the vehicle is running rough at idle with even a backfire type sound. On the road upon acceleration there is a noticable hesitation until I get up to highway speed. When traveling up a grade or hill the "hesitation" starts again until I reach highway speed. Not sure if it is a timing issue, a cyclinder issue, fuel injection issue, or maybe a mysterious electrical problem. The vehicle sat for approximately 3 years. I put fuel injector cleaner in it at the time of purchase with no change. I know the previous owner put fuel stablizer in it while it sat, and he did start the vehicle several times a month during storage. Any ideas on where to start. Thanks

 

There are probably lots of things to consider and check for but a good place to start is with new spark plugs, leads, distributor cap and rotor button along with replacing your fuel and air filter....

If these serviceable items don't lead to an improvement then the next step is to try cleaning the throttle body as it tends to gunk up with oil as a result of the EGR (Exhaust Gas Recirculation) system...