So out of the blue, my Titan quit starting. Check engine light is flashing and obd gave P0113 code. So after going over all wiring between MAS/IAT sensor, grounds, and replacing both cam and crankshaft position sensors. I found 4 of my 8 spark plugs (2 months old) we fouled. Replaced plugs, removed and tested coil packs, cleaned and tested fuel injectors, put everything back together. Still no start. No codes on obd, check engine light flashing. Smell of fuel in cab is present, Today I noticed a small puddle of oil on both sides of the truck under upstream cat. Located oil leaking from both valve cover gaskets, more so on bank two. I'm no mechanic, but I assume that would have caused the spark plugs issue, I'm gonna replace both gaskets but my question is would that cause my truck to not start? Also think exhaust manifold may be failing. I thought maybe head gasket but no smoke, nothing evident in the oil or under oil cap. Im at a loss and need help.