Oldsmobile/Buick Repair: Service Engine Soon Light, oldsmobile cutlass ciera, 1991 oldsmobile cutlass ciera

Question
Hello. I own a 1991 Oldsmobile Cutlass Ciera SL,6 cyl. 3.3 engine. I recently had a major tune - up done. Now it runs perfect.I am concerned about the SERVICE ENGINE SOON light soon coming on .It does that  about 3 minutes after I start and run it ,goes off for a few minutes, then comes on again ,stays on for a few minutes, then goes on again. my fuse panel is rather loose.could this cause
the light to come on like that?Should I be concerned?Thank you for your help.

Answer
Hello Elizabeth,
The fuse block is a possibility, but I doubt thats the problem.
It may just be getting a rich or lean signal for a longer period than it likes, and then correcting itself.
If the light goes off, then it isn't something that should cause you to park it.
Now, if it starts actually blinking, then there is something that you should get checked rather soon, but what you describe doesn't fit that.
That three minute thing is because sensor readings are not even used till the temperature reaches normal operating temperature, which would take about three minutes.
At that time, the oxygen sensor may not be warmed up enough to give a truely accurate reading, thus the rich or lean reading.
Then after the oxygen sensor heats up and starts sending a more accurate reading, it clears up the problem.
That is just one possible scenario.
If the light ultimately ends up staying off after all warms up, I wouldn't be concerned.
A quick check back with the place that tuned it up might be a good idea, especially if they can retrieve diagnostic trouble codes stored in the computer.
Van