Idle problem and jerking?

[69fastback]

The car is a 91 GT. The idle problem is that when you first start the car it will not stay running at all. You have to rev up the motor to get some heat in it before it will even stay running. Then when it does stay running it will sit there and idle at 800 for a second or two then surge up too 1700 and sit there for a second the go back down to 800 with out me pressing on the gas. It does this for a little while until it get up to about 150 dagress then it will stick to its 800rpm idle. I have heard that if the throtle body is dirty they idle bad good this be my problem or is there some thing else?


The other thing the car does is it has a jerking motion that seems like it comes form the rear. It is really werid cuz this only happens when i cruise down a road at a steady speed. When going the same speed for about a quarter mile or so the car will start to jerk until i step on the gas and then the car has no problems and just takes off. This only happens when I am going a steady speed. As long as it is under acceleration the car had no problems. When the car does start to jerk though the check engine light comes on and the oil pressure quage drops all the way down (it is factory quage) then goes back up when i step on the gas hard. Does this have anything to do with idle problem or is it different. It is an aod car with a shift kit and it shifts really nice. Any help is appricated i have no idea what to do about this.