Well Auto Zone said my service engine light was due to the engine knock code!!!!
I have been running 87 octane in it, and manual says we can run 87 and might be some noticable lack of performance.
I get NO pinging and car runs great!!
Going to have a mechanic (private) shop run a check.

How about ?
EGR valve
Oxegen sensor

Input greatly appreciated.

 

My 98 is throwing out a spark knock code and the dealer said their computer shows no spark knock. Go figure. I'm trying to find the time to leave it at the shop right now.

 

An easy test is to put a tank of good premium in it (like it's supposed to have) and see if the problem goes away.