My Lexus is Bucking

I have a 93 Lexus ES300 and it has 230,000 miles. I do routine tune-ups and just about everything has been replaced on a scheduled. Within the past week, I have redone my timing and reset it. My Lexus when it has sat for awhile, when I crank it up and get to going with Buck as if at a Rodeo. Once it warms up it will stop. I have replaced the Air Registry with a used one about a year ago and it stopped the bucking, but has started back up again. I am wanting to know if I buy a brand new Air Registry will that fix my problem or could it be something else. Please Help!!!!!

I found out what was wrong. The timing was off. Once adjusted that will fix the vehicle from bucking.