99 civic si problems

i have a 99 civic si. ive been having problems getting it started since its been cold. if the engines already warm, itll start. if not, it takes a really long time or doesnt at all. ive had to clean the spark plugs every week for it to start at all, because of the amount of buildup on them. when i try to start it, itll make some wierd sounds, squealling sometimes, and almost like a backfire from the intake. i bought the car this summer and didnt have a problem with it until it got cold. any suggestions? thanks.

when it is not starting, you need to check for power, fuel, and spark. work your way from there.

i have spark and power, but the fuel is an issue. if the car sits too long long, the fuel pressure gauge on the regulator goes down to zero. other than that, it reads fine, if i crank it, it jumps back up to the 30s/40s... not sure exactly what though. somewhere in there. and i also think its running rich, but not sure. the residue on the plugs give me this idea, also when it kicks into vtec it gives off a black smoke.... replaced the o2 sensor... not sure where to go from there.

Check the battery. Seems they will crank but not start when the battery goes bad.