Rpm jumping when cruising?

[99Gs-t_Spyder]

This is my first post so i apologize if I am doing anything wrong. I searched around a little bit but couldnt find an answer so if there's already a thread about this please feel free to link me to it. I have an auto gst and when i'm cruising at around 2000 rpm the needle jumps down to 1500-1600 and then back and forth. It accelerates fine and decelerates fine. I find my self having to accelerate and then coast instead of keeping my foot on the gas and staying at one speed. If i try to stay at 2000 with my foot on the gas for more than a few seconds the car starts to jerk a little after the rpms jump a couple times. Any ideas of whats causing this or help would be appreciated thanks guys

 

[o0GuitarKid0o]

Throttle position sensor comes to my mind

http://www.dsmtuners.com/threads/tps-sensor-voltage-problem.494377/#post-153530844

 

[o0GuitarKid0o]

If you have a logger you can log the tps % Or even the Voltage I think if you change the preferences in mmcd or what ever you have to log if you dont have a logger a multimeter will be your best freind although you'd have to remove the tps or get a freind to hold the gas pedal from closed throttle to wide open throttle and watch for holes (like 2000 ohms then 0 ohms then say 2200 ohms )in the tps when he moves the pedal, it's pretty much a potentiometer (variable resister)

Autos rely on tps for info to know when to shift ect..
so it makes sense that there might be an issue at a certain throttle position causeing your problem because it might think oh its at 30% and then al the sudden it could be 10% and then back to 30% in a matter of seconds

Here's how to test it http://www.oocities.org/motorcity/downs/7678/dsmtests.html its the second one

 

[99Gs-t_Spyder]

If you have a logger you can log the tps % Or even the Voltage I think if you change the preferences in mmcd or what ever you have to log if you dont have a logger a multimeter will be your best freind although you'd have to remove the tps or get a freind to hold the gas pedal from closed throttle to wide open throttle and watch for holes (like 2000 ohms then 0 ohms then say 2200 ohms )in the tps when he moves the pedal, it's pretty much a potentiometer (variable resister)

Autos rely on tps for info to know when to shift ect..
so it makes sense that there might be an issue at a certain throttle position causeing your problem because it might think oh its at 30% and then al the sudden it could be 10% and then back to 30% in a matter of seconds

Here's how to test it http://www.oocities.org/motorcity/downs/7678/dsmtests.html its the second one

I ended up testing it and changing it out today, took it for a ride and all seems well, thanks again for your help i really appreciate it

 

[o0GuitarKid0o]

Cool man glad it's fixed!