I have a 2000 RCSB Stepside.I am getting 13 mpg.That sucks,becuase I have a 2002 GMC ECSB that avergages around 16 mpg.The 2000 has a bog in the 2nd to third gear range.I do not have any codes.It is like it sucks air in the higher rpms.Any suggestion on what it might be.

 

Pluged cats

 

How many miles on the 2000?

 

It has 54,000 on it.I have changed the plugs,wires,fuel filters and cleaned the O2 sensors.I am going to have the tranny service next weekend.

 

ttt

thanx

 

Maybe an o2 sensor problem or your cats going bad.

 

I don't think a cat would be bad with that many miles but.........?

 

If it revs easily then the cats probably arent the problem. I would check the air filter changed the fuel filter change out the 02 sensors. The plugs should be fine they are good for 100k but pull them and check them out and see if they are running rich or if the electrodes are in good condition. Check the wires and make sure one isnt pinched or disconected. Also while you have the air filter out check the MAF and see what kind of condition the wires are in and if you have taken the screen out put it back in there it is there for a reason. This may sound like a stupid question but when was the last time you changed your oil? Last but not least if all the other stuff doesnt work pull the y-pipe off and look at the cats and look and see if they are clogged look for the catalyst looking like a rock or if something feels loose in there if there is something rattling around in there then you need new cats.

 

I am going to check all my vacuum lines this evening and see if any of those are bad.

 

I had the oil change about 500 miles ago.I have cleaned the K&N filter and I cleaned the maf sensor.I have already put the screen back in.I think it my a have a vacuum leak somewhere.I have check before for a leak,but could not find one.I idles fine,but it does not have any power like it use too.I can stomp it and it goes,but it should light up the tires.I will not spin the tires.I do have a cat back and a K&N filter,but that is all.Everything else is stock 4.8.