inconsistent functionality with LIKE operator

I'm using PostgreSQL version 7.1, and I'm having trouble with the LIKE
statement.  How would I find the value "a\bc"?  I tried using the
backslash to escape it: LIKE 'a\\b%';

If I specify: LIKE 'a\\bc', then it works, but if I wanted it to look
for consecetive characters after the c, using the %, then it returns
other values besides what I'm looking for.

I also have the same problem with percent (%).  I have a test string
with the value "ab%c", and I want to look for that using LIKE.  I tried:
LIKE 'ab\%c', LIKE 'ab%%', and LIKE 'ab\%_', but these statements not
only returned what I was looking for, but also other values:
"abc","ABC", and "Abc".

Phuong