My 2000 Ram 1500 5.9L is idling rough. I checked the codes and the only one up is P0138 bank 1 sensor 2 o2 sensor. I have order new sensors for it both front and rear. I have also done all the tune up stuff already. Plugs, wires, cap and rotor. Will changing the sensor help it out or could there be some under lying problem making that o2 sensor read bad? Any help would be appreciated.

 

Had the exact same issue, though I did not have a CEL. I pulled my Upstream O2 sensor and it was filthy as sin, replaced it, bad idle gone.

I would say yes, new O2 will fix your issue. Though you probably only need to replace the Upstream (Pre-cat) O2. The Downstream (post-cat) O2 only measures emissions and has no effect on how your engine performs. The opposite is true for the upstream.

All that being said, have you checked your Plenum? Blown plenum can quickly foul your O2 sensor, and your catalytic converter.

To check for a blown plenum gasket:

Remove air box, open throttle plates all the way. With a flashlight, look down into the intake. if you see oil pooled in large amounts, its toast.

 

Remove the TB to look for oil pooling, so you can see in all four corners inside the intake. Looking through the plates is NOT how to check, and a waste of time.

 

Hey I'm new to this site. I'm having rough idle issues on my 2000 Ram 1500 quad cab 5.9 4wd. I have replaced the plugs. All wires were good except cylinder 7, where the wire was shot and a misfire was detected from my code reader. I replaced cylinder 7 wire and cleared the code. I have tried idle air control valve sensor and that wasn't it so i put the old one back on. I also tried the one on right side of air cleaner, farthest back on right side and that wasn't it. Keep in mind i have not replaced cap and rotor. Any clues as to what can be causing this would be greatly appreciated. I know it has to be something minor, it's just really irritating. Please respond with any ideas as to what to try. Thank you

 

Why not just spend $15 and 15 minutes to replace the cap & rotor? Also wires should usually be replaced in sets, unless they're fairly new, and in that case you needa make sure that they're wired per the TSB (someone here should have a link for it).

Did you clean the throttle body while you replaced the IAC (you should've)? Did you replace the TB gasket each time the throttle body was off (also should've)? Make sure you had the 4 bolts on the TB tight.

Spray carb cleaner or similar product around the vacuum lines at the intake while truck is running, if the RPM changes when you spray a line, replace it.

Also read the "end-all be-all plenum thread" stickied on the top of the forum page.

edit: oh yeah, did you have the negative battery cable disconnected when either the TPS or IAC was replaced? If not disconnect it for a few minutes, then hook it back up... Drive around for a while so the PCM can relearn the new info.

...And welcome to DF