2000 Silverado Idle

I have a 2000 Silverado with 5.3 4wd ext cab with 120,000 miles. It just started to idle rough. Almost like it has a nasty cam in it. Recently I have been getting 18 or so mpg and now down to 12mpg. Doesn't matter if it is hwy or local. I have changed the fuel regulator,fuel filter 8,000 miles ago. I also have a clunk when you pull out from light or stop sign. I was told that I needed to grease it up? It sounds like it is coming from the drive shaft or the rear. Also when in OD it feels like it is surging but the RPM's don't move. Does not do it in D just OD.

As far as the idle quality, did you clean the Throttle Body?

//2000CAYukon

I have a 2000 Silverado with 5.3 4wd ext cab with 120,000 miles. It just started to idle rough. Almost like it has a nasty cam in it. Recently I have been getting 18 or so mpg and now down to 12mpg. Doesn't matter if it is hwy or local. I have changed the fuel regulator,fuel filter 8,000 miles ago. I also have a clunk when you pull out from light or stop sign. I was told that I needed to grease it up? It sounds like it is coming from the drive shaft or the rear. Also when in OD it feels like it is surging but the RPM's don't move. Does not do it in D just OD.

I would have the engine codes pulled dtc...this appears to be a cat plugged problem possibly...have you replaced the upsteam O2 sensors ...they are only good for 100,oomi...this can damage the cat...


poor performance and a drop in MPG is usually this area...get readout of the O2 ...this will give good direction as to your problem..


I have same vehicle same mileage...tranfercase fluid replacement solved my clunk noises...on starting from stop it would clunk..

on your throttle body and IAC I have cleaned these parts several times to maintain a correct idle and to keep the throttle plate from sticking ...

I have the shop manual for this so if needed i can send you privately some tech data...