I got a p0336 on my 96 fwb. I switched it out and got a new ac delco brand. Code went away then driving the car around for awhile and the engine light came on and its the p0336 again?? So i went under the car and took the sendor out to inspect it and the wiring. I found out there was oil on the backside the inside of the casing part sensor? Is that normal?