03, Trailblazer 4.2L, ruff idle in gear or with a/c on.

[carriedi]

oh, on the frozen O2 sensor:
I have a dozen or so, O2 sensor wrenches or sockets. there are all sorts of angles and obstacles in the way to get at the O2 sensors. Getting at them is half the battle. If you can get a good grip on the sensor and have room to turn it but it is just froze up solid you may have to use heat to get it out. I have a mini-inductor that uses electric current to get the sensor hot. Red hot without puting heat where it may do damage to other things around the sensor. Sometimes when the sensor comes out it may damage the threads. You may have to re-thread the hole. Heli-coil or put a new bung in the pipe.

you can try some kind or rust penetrating fluid and let it set for at least 20 minutes and see if that helps.

[carriedi]

this vehicle should have a misfire counter that could pick up misfires that may not set a code yet. Graphing the cylinders you can see if certain cylinders are missing on the rough idles and concentrate on those cylinders. Move coils, spark plugs, injectors, check your crank pulley, make sure it's on tight. Rather than just putting parts on to see if that does it, take it to a shop that can diagnose something and then see if you can fix it. At least now you would have something to back up putting parts on.

[carriedi]

something that could affect your idle too is having a problem with your AC. Make sure your ac compressor and clutch are working okay. I had a truck that came in with the ac clutch that was broken. It was way off balance but it still turned on. It vibrated like crazy as you speed up.