does not start

The other day my mother was driving her car and it started slowly accelerating until it finally cut out on the side of the road. I came and got her. Before we called a tow truck driver, I checked for obvious signs of a problem. It turns over well, it just does not start. I tried to jump the vehicle, even though the lights seemed bright. I pulled the battery and took it down to have it tested. It tested good. We then had the vehicle towed back to my house. I removed the alternator and had it tested. It tested good. I removed the back seat to listen to the fuel pump. It sounded healthy and seems to kick off as it should.I have not check the fuel rail pressure or injectors. I did check the the ignition coils. All four tested good. The spark plugs all looked good, but the fourth cylinder spark plug had a lot of oil around it, like a bad seal. I then checked all the fuses. All of them were good, in both the engine compartment and cab of the vehicle. Where should I look next?
Thanks,
Bryan