|Subject : Terrano running slow when check engine light comes on|
read this forum from beginning to end. the cure for Your problems starts with a scan of the OBD2 computer that is in your vehicle.
The codes will tell you where to start looking for a solution, and this forum has lots of previous experience on file.
Please read it.
P.S read about the No1 injector lift sensor for your engine problem, and think about draining and replacing the auto trans fluid (if you drop the pan, replace the filter as well).