Prelude

engine 燈著 doesn't must mean engine has problem, but it can.
Most car can be checked for code meaning in some way without OBD2 reader.  But of course, it's better to have OBD2 reader, a decent one can cost $150+.

Any noise?  Any stutter acceleration?  Change spark plug?  Oil change?

Prelude

You said it stalls sometimes?

If that's the case, it can be cylinder misfire.  Pretty common for old cars.
Check the code first.

Why can't you check the code yourself?
http://us.lexusownersclub.com/fo ... index.php/t441.html

Buy OBD2 reader from Returnable place, or borrow from some friend.