'92 hyundia excel carbeurator problems

I have a 1992 hyundia excel and am having problems with getting it to idle smoothly, and also preignition occures too, Question can low octane fuel cause pre ignition and also cause poor idling, it otherwise runs well and
has good compression,new plugs, starts good, it is a 1.5 liter engine, any help would be appreciated, thanks.J.
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