Reply To: RE: Rough idle

New Topics Forums General Discussion 1999 – 2002 Nissan Quest Rough idle Reply To: RE: Rough idle



Maybe this helps:

At left side of throttle body and below the cam that controls the butterfly flap of the throttle, there is a thermo-element that controls the fast idle cam. When the engine is cold, a pin in the thermo-element is contracted and the cam is in a position that forces the butterfly flap to be somewhat open allowing more air/fuel to the engine. As the engine warms-up, the pin in the thermo-element extends moving the fast-idle cam to a position where the butterfly flap closes (goes into normal operation position) allowing less air/fuel. If the thermo-element is damaged (fully extended) or not calibrated properly, the butterfly flap will not be open enough for allowing more air/fuel when the engine is cold. This is reflected in the engine RPMs. Higher when cold, lower when hot.

There are two marks in the fast-idle cam. The cam has an adjustable screw that makes contact with the pin of the thermo-element. When cold, the cam follower lever, which is a roller on top of the fast-idle cam, will be aligned to the most left mark of the fast-idle cam. When the coolant temp is about 167-185°F, the cam follower lever should be aligned with the most right mark in the fast-idle cam.

Check it out and report back.