I have 1997 GMC SUBURBAN V8 and the service engine light keeps blinking and she runs rough in park in idke and in . Yesterday i changed the plugs and one of them had oil in it please help

No Bueno... Bad rings... time for a new motor... or a rebuild

I would put a scanner on it to see what codes pop up, could have something to do with the pcv, and or emissions. Other wise do a compression test on that cylinder, it should be 150-160 lbs.

That's coming from your spark plug tube seals being no good and the check engine is because the oil on the plugs which is also causing the rough ride. I would suggest getting the tube seals replaced along with the valve cover gasketshould solve that issue for you, also replacing any spark plugs and wires that had oil on them. Hope this helps

Don't throw good money away. First, clean and regap plugs. Check air filter, can be shaken and tapped lightly to remove most dirt , can use carb cleaner if available. Check fuel filter, if you can remove, guessin probably in line, try to blow air through same way as gas flow ,if very restricted after blowing all gas out , replace. Also, while you have spark plugs out , put maybe 16th of a cup of trans fluid in each cylinder , just let sit while doing all other services and checks. Will not hurt engine. Might smoke for a few min after starting, but will clear up. Check to make sure you are getting spark to all plugs,,oil in it, maybe it wasn't firing. .oh, also check pcv valve, clean with carb cleaner, must rattle freely. Good luck 96vaner also try seafoam in your gas at next fill up,,,,very firm believer. One more, also check all vacuum lines

Mine was blinking at me too but changing spark plugs worked