What caused this problem?
on 2002 Kia Spectra

My engine light came on flashing,used scantool got misfires on cylinder 1&4

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2 answers
Usual culprits are: spark plugs need changed, spark plug coils are going bad or you got a tank of bad gas with water in it. Try some fuel system cleaner in your tank and then watch to see if engine light returns. If so, refer to the first 2 possibilities.
csubak30 is on the right track with what parts may cause this issue. There are others. However, the main concern is that the light was flashing. A flashing Ck engine light not only indicates misfires, but the flashing aspect indicates the engine is misfirig badly enough that it could cause damage to the emissions system, more specifically the catalytic converter due to the significant amount of unburnt fuel. The flashing indicates that at that moment the problem is serious enough to cause other significant damage to the engine or components.