I had this about a month ago. Says a misfire on cylinder 5 and 7. I had the spark plugs change and Advance auto parts erase the code. I changed my oil last week and put some serpentine belt conditioner to my belts( bad idea made the belt more noisy/squealing sound) then the CEL light came up. Went to the local Advance auto parts and checked again it was the same codes. Do you think I have to change the ignition cables for the mentioned cylinder? Maybe somebody can give me advice before I buy the ignition set which is expensive about $ 55 each and I will need about a total of 4 for the 2 cylinders. Thanks in advance for any suggestions.