starting hiccup

[mpj76]

During cold starts, my car usually starts right up with no problems but occasionally does:

1. Starts up after about two seconds of cranking.
2. IMMEDIATELY after startup RPM'S drop and the car "coughs" while idling erraticaly in the very low RPM range (<700). Almost like the timing was way off after a dist. is installed without marking. It almost dies.
3. It will cure itself and return to normal idle in about 3 seconds.
If I tap the throttle it goes away faster.

I cleaned my idle air valve and mass air meter. It has helped a lot but it still does it sometimes. The smog pump is removed and the AIR tube is capped off. The heater core is bypassed. O2 sensors have about 35000 miles on them. Could this be a sympton of a bad TAB/TAD solenoid? What are they, and what is their function? Car has 150K miles. I have new plugs, dist., coil, wires, and MSD 6. The problem existed before and after all the new stuff with no difference. Also, sometimes my starter free spins without cranking and then all of a sudden catches hard after I stop cranking. The fly wheel is not original but the problem started a long time after its installation (50K miles ago).