Ive had the car for 1 1/2 (mother had it for 4years before me) years and have never had any major motor problems. Its a 350 TPI roughly about 80k on the motor.......and its not driven hard(see's 70mph on limited freeway trips)

When im driveing down the road on the way home there is a road I take thats about a block long and the speed limit is 15MPH. I drive about 30mph roughly a spot between 30-35mph down the road and at that speed exactly the car has a slight jerking that it does. If I slow down or speed up it stops and I have no other problems with the car what so ever. Its very confusing and I want to know if anyone has any idea what it may be.

 

Sounds VERY symptomatic like a torque converter lockup issue. But lockup issues usually happen at 40 mph, not at 30 mph....

 

I had a 89 Trans Am 305 TPI that did the samething around that speed, I thought it might have been the tranny, but found out the temp sensor was bad and was flooding out the engine. Got new sensor put and and ran perfect, it also would idle rough on start up before the fix.