With my 1989 RS. When I first got it, it ran perfect all the time. About a month or so later, I was going down the interstate and when I got up to about 70mph it jerked pretty bad. It scared me and I still don't know what it was. For a while it would only do it at about 70mph. And if I hit the gas when it did it, it would hesistate and the run fine above 70mph. I gor worried about it and parked it for about a week. Then I missed it and started driving it again and it ran fine for a long time then all of a sudden it started doing it again, but not at 70mph, instead at ANY mph. But when it does it at about 70mph it is one or two good jerks, when it does it going slower it is more like sputtering kind of. I don't know how to describe it any better. Any suggestions?

 

misfires can be caused by alot of things. is the service engine light on? have you done the routine maintenance on it lately? spark plugs, wires, distributor cap, rotor, air and fuel filter? alot of times the fuel filter will be the culprit. sick

 

I have done everything I think except the fual filter. I really hope that's the problem, thanks. Oh, and the service engine light comes on sometimes when I drive it but not all the time.

 

That check engine light is telling you a code is stored. It will go out after a while but does not mean the problem went away. Change your fuel filter and check the code.