hey guys have a range rover county 4.2 liter. installed aftermarket distributor. ( not sure if related) on cold start up when cold outside engine rpms fluctuate up and down drastically. once vehicle is warm there is no issue. has new maf sensor new idle air control, base idle is set. good spark and fuel pressure. Almost acts as if engine spark timing is being retarded drastically and then back to normal. any ideas will be greatful. or if anyone has experienced this

 

Was this happening before you installed the aftermarket dizzy? Not sure what type of distributor you have, but was the timing advance set correctly? That's the only thing I can think of, maybe its very sensitive?