1999 Plymouth Grand Voyager "car jerky idling along" Questions

...idling, accelerating from being stopped can be really jerky, and the temperature gauge has quickly gone up and down (up to about halfway). It's an intermittent problem - sometimes everything ...

...car running better than it did before you replaced the fuel pump?  I am just wondering what tests were done before the fuel pump was changed.  There had to be a reason to think the old pump ...

...jerky. Buick's is smooth as a butter. What should I do to make this go away? Start with spark plugs? I don't know if the dealer has serviced it except oil change and detailing before the sale. I mean ...

...car does not like being sat at set revs, cars with the CAT on it's way out usually like to either be accelerating or decelerating not sitting at the same revs as you get that jerky feeling, thats one ...