Elantra has erratic rough idle

[S.I.Lou]

Hello I,m new here. I think i,m in the right forum,if not let me know. I have a 2005 stock Elantra with a erratic idle that when i'm at a red light waiting for it to change with my foot on the brake, the RPM's rise to about 5000 rpm's without touching the gas pedal then it goes back to normal on its own. Then sometimes it seems like the engine is going to stall. It does not happen all the time.If someone can give me some info on this before i take it back to the dealer i would appreciate it.

[Whiplash_89]

Its most likely you ISC. When the pedal is all the way up, the throttle plate is all the way closed, and the engine idles. The idle switch is triggered by a small lever connected to the plate inside the throttle body that regulates the amount of air entering the engine. When the idle switch is open, the throttle plate is at least partially open - when the switch is closed, the throttle plate is closed. Your idle switch is acting up, causing it to open when you dont have your foot on the throttle.

[cclngthr]

A better idea is to get the codes read first. A bad TPS sensor also causes this issue.

[S.I.Lou]

Thanks for the info.