Hi guys first post on here, just bought a new sierra on Saturday, and when I was driving it home I noticed it was completely dying out at junctions ect when I was dropping to idle quickly, plus if I was cruising along at 60/70 and let off the accelerator I was getting a bit of a noise as if I wasn't getting a good running mix.. The only thing I've noticed is that the sensor on the side of the air flow meter (the name of said sensor would be handy) doesn't look like a great fit but it does seem to be sealed correctly.. Could this sensor be my problem or is it something more common?

 

It sounds as if the base idle isn't set correctly. With the idle speed control valve disconnected, the engine should run at 600 rpm. There is an idle air bypass screw on the throttle body, facing forward, next to the throttle position sensor.

It could also be the vehicle speed sensor not working, this tends to allow the revs to drop when you pull up to a stop. On a RWD car, this sensor is located on the side of the gearbox, near the back. On 4WD versions, it is at the bottom of the speedo cable where it joins the intermediate shaft through the sump.

If you lift off the throttle, the fuel is cut off above 1700 rpm, to reduce emissions and improve fuel economy.

 

Yes mate I think you've got it, my speedo doesn't work so I'd assume that as good proof the speed sensor isn't working. Is it a hard thing to repair?