Bought a 97 rs v-6 automatic 116,000 miles on it 2 months ago. When I try to do the speed limit (usually 55) the tachometer bounces back and fourth between 1700 and 2000 rpms. Its like the car saying "I just dont want to go 55". At that point I can decelerate to like 52 or accelerate up to 58. When it is bouncing around I usually step on the gas and it shifts gears and gets going imediately. I was wondering what your opinions are.
I didnt tell this guy that I had any issues but somebody whom I was told was an expert suggested I use seafoam to clean out the engine. Any thoughts on that as well?

 

i was thinking egr valve
usually they get peices of carbon jam them open , so i guess this sea foam must help to flush out the gunk and stuff.
buy the sound of it it may have a vacuum hose leaking maybe, causing the egr to open erratic when it sould be open steady at cruise

 

so it's the accual rpm of the engine surging, not just the needle jumping around.
they would be more electrical

 

Have it scanned for codes, might be throwing a tranny code. Sounds like it it trying to shift between two gears at that speed, and can't make up its mind. Put the car in 3rd gear and see if it does the same at 55.

 

if you got the scanner on it ... check for miss-fires,
good point about the shifting, if there is a bit of miss fires it will make the tranny shift up and down at certain points.
also you can check the egr valve desired and actual position with the scanner and even comand it open and closed to see if it sticks

 

I do not have a scanner to hook up to it. When I bought it no check engine light was on, within the first week it poped on. It was at a garage they hooked up a scanner and all the codes got cleared out and no light is on now. I noticed that if i go from a complete stop and accelerate fast it stays in 3rd gear until like 90mph. If I do the same thing with normal driving and take the speed up to a little over 55 then let off the gas it shifts to lower rpms then when i step on the gas lightly it does the rpm needle bouncing thing and only when I step on the pedal hard does it shift and accelerate quickly and take off. I hope this makes sense. So as i drive normally i take the car up to 57 mph let off the gas the car shifts I eventually step on the gas to go a little faster then the rpm thing happens, I step a little harder and the car shifts then accelerates fast.

 

that's what i was seeing in my head, but just to be sure ... as the needle is doing the thing... the car is basically bucking/shuddering , and accelerating poorly, until you give it a little more gas and it goes normally?
sure sounds like it is struggling in overdrive at low rpms when your just cruising, most likely plug or wire. after that start to check for injector slightly blocked , egr sticking , vacuum leak