My '87 E16 Sentra Coupe still cannot be started. In the last week I have changed the distributor cap, rotor, plugs and wires. When I try to start it, she just turns over but I can't get any RPM's to register but every so often. Finally today while I was making sure that I was actually getting spark, I noticed a pretty heavy amount of oil residue on the spark plugs(top and the threads). After consulting Haynes, they say that this is due to either worn valve guides or piston rings. I'm wondering how much this will cost me to correct this and what my options are. Is this reason for hard starting or hesitation? I'm still thinking that the injector is bad and there's a fuel system problem. ( $196 for the injector at Advance Auto) Any way to check the injector without the car running??? That's expensive to replace if it's not needed. I mean i'm getting spark, I assume it's gotta be the fuel. HELP.