96 XJ 4 cyl, have a set check engine light, code 27. All I have as symptoms is a rough idle at times and also intermittent part throttle hesitation. otherwise it runs ok.I can't find any diagnostic info except "requires tech diagnosis" Is there anything I can check on this at all? or do I need to get it to the dealer? It is high mileage but otherwise ok.Any ideas would be appreciated.I guess I'll have to get a factory manual to go further!Could it be a leaky injector or a bad one? Light does not go out.