Fuel octane/check engine light
 

About a year ago I kept getting a code in the check engine saying fuel injector 7 port stuck open. So we soaked and cleaned the injectors and everything was fine.

If i put anything other then 87 octane (reg) in the gas tank, that same code pops up after about 25 miles. Ive done this 3 times to test it. If i put 89 or 91/93 premium in the tank, the check engine light comes on and remains on with that code.

Then when i switch back to 87, after a few days the check engine light goes off and stays off unless i put a higher octane gas in it again

Why would the octane in fuel cause this to happen?

ALSO! whenever that code is "tripping" I find that the oil smells like gasoline and have to change it. so its not just a false code

Faulty fuel injector pouring fuel into the cylinder, i doubt fuel choice would cause a injector problem, if anything i'd say either bad injector or connector

Most likely the amount of additive in the fuel you are buying. Replace the injector and replace the spark plugs with Champion Regular Cooper Plugs, yes the cheap ones. Remember to gap them.

it went 5 months without tripping the code, so i did the higher octane test and sure enough that caused it. I stuck with regular and its been 3 months and counting since it has come on. The only times that has ever come on has been when i ran the higher octane. Thats why its odd. someone mentioned an O2 sensor causeing a problem on that port

You can cheack the resistance through each of your injectors. IIRC they are supposed to be right around 12 ohms. Other than that you would need a lab scope just to be able to diagnose the issue but it sounds like inj #7 is a problem.