i had exactly this issue. I'd got very lazy, mostlyh through not working with a teacher or playing with anyone else who would have picked me up on timing. The only solution I found was to go back to basics and learn timing from scratch, with a metronome.It takes a certain amount of guts to admit you have a problem and you're through that stage.
I used to listen to records at work on headphones and really listen for the drumbeats and tap along. Then I'd listen for the bass line and tap that out whilst thinking about the drum beats. This helps break up the metronome monotony.I did some drummer tests online, where you hear beat one of bar one and have to tap out the other beats and you get scored on how accurate you are (yamaha site, I think, but try google for others). You get better (at that part anyway) a lot quicker using those, I found.
Obviously you also need to train your hands as discussed above, but training your head is important first, in my humble opinion.