The spark plugs are underneath that cover on top of the engine (on mine the cover says VVTi). Just take that cover off, and then you will see the four ignition coils. Take off the four ignition coils (with igniters), and you will see the four relatively long holes underneath, and the spark plugs are at the bottom of those holes. You will need a good spark plug socket (preferably a thin wall socket) and a 6" or 12" extension.
On top of the engine, but you have to remove the cover to see them.
http://echodrivers.com/forum/viewtopic.php?t=4605url
The Toyota echo does not have wires or a rotor, each spark plug has its own ignition coil (coil pack). So really, all you can do is change the spark plugs.
Don't fix them, replace them. Its an easy job, see related link.
http://pdftown.com/2000-2002-Toyota-Echo-Service-Manual.html
The 2002 Toyota Echo OBD 2 port is under driver side dash next to kick panel
For my 2002 Echo it is 3.7 Liters with a filter change.
3.6 liters
To flush the coolant in a 2002 Toyota Echo you will need to drain it first. Flush with fresh water and then refill with coolant and distilled water.
The water could be coming from a coolant leak higher than the plugs on the engine. Look around the head for signs of any leak as it is possible that there is a head gasket leak.
See related link.
i have a 2001 and it gets about 39-42 mpg