Why would oil be in the spark plug hole causing misfiring and the 'check engine light' to come on on a 1999 4 cylinder Toyota Camry?
There are seals in the valve cover that over time can detereorate and cause oil to enter the spark plug tubes. This oil can then seep between the plug and the wire which can make a better path to ground then the spark plugs gap would and cause a misfire. answer The bottm oil ring on the piston could be broken and instead of that ring wiping the oil off the cylinder wall as it goes on the down stroke, the oil is still on the wall and then egst pushed to the top and included in the combustion chamber. The oil will foul the plug and yes it will set off a msifire. Get a compression check on all 4 cylinders and see what reading you have. All it is is a pressure test. There is a pressure gauge you can buy and screw it into the spark plug hole and get readings yourself if you so wish.