Sc400 Jerks Badly When Trying To Maintain Speed Of 45

[Leob]

i have a 93 sc400. operates well, but when driving and trying to maintain consistent speed car jerks badly but if i accelerate, no problem. This seems to only happen when the check engine light comes on. I had the cel code read and it is saying knock sensor. is it possible that the knock sensor is causing the jerking or the fact that the cel appears to take half the power of the car? thanks in advance for any suggestions and advice