None starter

[ramzb]

In the 18 months that I've owned Silvia the only distance I've driven it is from the workshop to outside. Today I drive her outside to finally buff and polish the clear coat, when she started the engine was missing quite badly, went to start it this afternoon and the engine turned over OK but would not fire, took the plugs out and all of them were covered with what looked like thick black sludge, cleaned them off, put them back in and it still wouldn't fire. The plugs are new and were put in just before Xmas. Not being to hot on mechanics I need some advice on what the problem could be.