Why does my service engine soon comes on in my 1994 Pontiac Grand am?

[Kerry K]

It only will come on when it is idling for example at a light. When I start driving again it acts jerky until I stop and then it goes off. I know I can take it in and have a mechanic diagnose the problem but I want to know if anyone knows offhand what may be causing this or what I may need to get fixed. Just curious.

 

[bandit_60]

try cleaning out the throttle body inside with throttle body cleaner. it might also be a 02 sensor or the egr valve.what ever it is have it checked before buying a whole lot of stuff you might not need

 

[Loonerone]

Could be a myriad of things.
Could be Ignition bits and their sensors.
Run a few tanks of Premium fuel and some decent Injector cleaner after cleaning (if needed) the throttle body internals.
You can as well try some Marvel Mystery Oil added to the fuel.
Sometimes fuel stations add some water to stretch/increase their fuel profit which will cause problems with idling and of course performance.
Buy fuel at busy places because of turnover in the ground tanks having less probability of generating condensation.