My car threw a P0121 code last week and was idling around 2800 rpms. I checked all the connections and cleared the code and the next day everything seemed fine. Later on that night it did it again although it didn't throw a code. Now it seems like it will idle perfectly in the daytime when it's 60-70 degrees and idles super high when it's 30-50 degrees at night. I just want to make sure it isn't a small issue before I think about replacing the sensor. We already made sure all the vac lines were hooked up proper, especially the ones to the intake manifold.

 

Could be an idle control valve. You can test the tps sensor

 

do a sweep on the tps that will tell u if ur tps is good or not.

 

thanks for the replies guys, i'll check it all out today