1998 Mazda 626

Electrical problem
1998 Mazda 626 4 cyl Two Wheel Drive Manual 126000 miles

my mazda has on all been very reliable but I have developed a problem with the engine it seems to run ok for a few miles then what seems like a misfire.I changed the spark plugs and the problem seemed to go away for about 5 miles then now it has come back but not as regular as before. Mainly when driving up hill in second gear it seems to misfire. Any suggestions would be welcome as to why it is doing this. Thanks
April 14, 2008.

You need to scan the computer for code/s and comeback with it this is where we start.

Apr 14, 2008.