Which sensor is it?

[intimidatordei]

My 1994 4.3 Vortec VIN w with CPI runs great after it is warmed up, but prior to reaching operating temp. it has an extremly rich exhaust (very black), rough idle and surges. The surge is more of a stumble as if it is going to quit then takes off again. Once the engine is warmed up the idle smooths out, the black exhaust goes away and engine has plenty of power. I am certain this is a sensor related problem but not sure which one. Thanks for any ideas or help anyone can provide.

[sreve]

check engine light? mileage? state of tune? what have you done so far? happened all of a sudden? more info.

[intimidatordei]

The engine has just been rebuilt and has about 70 miles on it now. It was doing this prior to the rebuild but now it seens to be worse. I am just trying to avoid buying sensors I realy don't need if possible or just get started in the right direction. The engine seems to run good ounce it is warm. I had 1.6 ratio rockers put in, K&N FIPK intake, Ravin muffler, and high flow cat. I also have new ignition wires, cap, rotor, and coil all Accell. Thanks for any ideas you can provide, because I can't seem to get going in the right direction. Also the rebuild included a three angle valve grind, the block was bored .030 over and all new parts were used.

[sreve]

k&n oil can srcew with the maf clean & retry. does the check eng light come on key on eng off. should spit a code as rich as it is.
is it hard to start cold?
a good scan looking at live data sounds to be the next thing if the answers are yes and no respectively.

[intimidatordei]

Thanks for your help and ideas. Since my truck is a 1994 it still has a some what "old school" distributor so I've been working with the timing. I,ve got it advanced 3 degree's and the engine is comming to life. I also thought the MAF senser could be the problem but my truck doesn't have one, I guess in 1994 this model didn't use a MAF sensor. I did have the IAC and ECT sensors checked out and they are all good. If you can think of anything else send me a PM. Thanks again for your help.