I own a 1995 Toyota Avalon, that has 171k miles on it. The problem I'm having with it is that it started to idle rough and there's a misfiring sound that's noticable from the exhaust tailpipe, consequently the check engine light lit and remains lit. I figured that maybe the cause of the problem was the spark plugs, so I changed them but the problem remains the same.
What other things should I consider or check for to resolve this problem? Or, what do you think the problem is or maybe?