Rough Idle and Screaming nose from engine ? PT II

[240sohc]

Originally Posted by Hashiriya415

You don't need it. All it does is heat up the cat when you start your car cold, that is the only time it works.

agreed...you only need it for smog. however, the pair valve is supposed to send clean air into the exhaust to help lower the NOx emissions. if the pair valve gets dirty it can introduce exhaust back into the intake causing rough, roaming idle, bogging, and stalling at low rpm. so you can clean it up or just remove it and plug up the bung on the exhaust pipe. nissan dealer even sells the plug.