Oldsmobile/Buick Repair: Oldsmobile Check Engine Light, lean mixture, vacuum leak

Question
What would cause the check engine light to come on and off while driving the my car?  I have an 89 Olds Cutlas with 137000 miles.  Runs well until the light starting coming on.  It bucks sometimes while driving and some times dies out.  I have checked the air filter and it appears to be clean.  Is there a PCV valve that needs changing?

thanks for your help.

Jim Wozny

Answer
Hi Jim,
Sorry this answer is so late...I signed out on vacation, but the site doesn't seem to update all the areas I am in, even though it says it will.
There are a whole stack of things that could cause that. It could be getting an oxygen sensor reading from a rich or lean mixture, which could be caused by the air filter, which you checked, or the exhaust restricted, or the plugs dirty and not firing the mix completely, a vacuum leak, etc.
The EGR valve closing on some carbon occasionally, could cause it.
There is a PCV valve, which should be replaced once in a while. The EGR valve should be removed and cleaned.
Some injector cleaner in the gas tank might be all that is needed.
Van