Check the cap and rotor. Are you burning a lot of oil? How's the plenum gasket? Take a peak down the throttle body.

Can you post the codes? The P#'s?

 

How do I check the cap and rotor

 

Take them off and look for burn marks or evidence of arcing/flashing over. Make sure the rotor and all the contacts aren't burned.

 

i changed the idle air controle valve with abay part awhile ago..if that not working wright will it make the motor run rich? maby.. i cleaned the thotle body and it looked pritty gumed up so i replaced it

 

The IAC is basically a controlled vacuum leak. It has no effect on the mixture.

Mixture is controlled by the PCM - by varying the injector duty cycle. It uses a number of inputs, engine temp, MAP pressure, RPM, load, O2 sensor inputs, etc.

The upstream sensors provide inputs for mixture, the downstream is for monitoring catalyst efficiency.

 

the truck burns almost no oil between changes. from what i read i think it the cap or bank one upstream o2 sensor. i got a small vacume leak but i think its from the filler hose to the gas tank. it rusted out a bit. i sprayed carb cleaner around all the hoses under the hood and around the trothel body and no change in idle so i dont think the leak is there. i ll check the cap tomorow

 

Please post the P-codes. If your scanner doesn't, just do the key-dance to get them in the odometer window.

You're describing an EVAP leak, not a vacuum leak.

 

po 300, 306,304,302. every time i scans it i gets different cylender codes. never got the running rich code this time. i reset the codes last time i was at it. i just started it up to get the codes that i just gave u

 

You might also want to check the fuel pressure.

 

After getting a code on every cylender I don't think it's the o2 .