I'm not sure how to check an O2 sensor. I do know that they need to "heat up to temp" before they start doing their job (assessing the exhaust contents and then sending a message to the computer to adjust richness/leanness). This might explain your worse idling after 10 minutes or so ... it has taken time for them to warm up ...
I think its safe to say that replacing the sensors after 100,000 miles is not unreasonable. I'd start with the one after the cat converter. On my truck you need a special tool (you could probably rent one). It is essentially a socket with a long slit in it. This will make sense when you get under the truck and look at it. New sensors are approx 60 - 80 bucks a pop.
Also, have you cleaned the Intake Air Temp sensor? It should be in your air intake duct between the air filter and the air intake ... probably in the duct itself. It could be that this is the same thing as the Idle Air Control Valve (any experts out there??) that you mentioned. Anyhow,clean the sensor and check the wire harness connections and wires. This sensor of course responds to temp which might explain your worsening idle on the highway problems (cooler incoming air). Maybe a "long shot" but it's worth a quick check ...
Also, its possible that your Throttle Position Sensor is dying or shot. A broken or loose TPS can cause intermittent bursts of fuel from the injector and an unstable idle because the computer thinks the throttle is moving. I'd try another clean with the Throttle Body cleaner first ...
Also, if you have one, Air Pressure sensors are usually located near the throttle body on the intake manifold.
Plugs gapped correctly?
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Originally Posted by 90gmcmoneypit
I have not checked or replace. How exactly do you go about checking an O2 sensor?
Checked, checked, rechecked. I had one that came up from the wheel well very near the battery that was clogged. Fixed. Still idleing rough.
EGR was fine. No immediate concern, just a little surface carbonizing, and no clogs in the intake.
I don't know if this model does have a air pressure sensor or not, and if it does, I have no idea where it's at. I've also been trying to locate an Idle Air Control Valve with no luck. Any ideas or knowledge would be appreciated.
This problem, literally, just happened. One second it was fine, the next it was idling horribly, stalling, ect. It's not like it was a gradual issue, and it only occors after the vehicle has been running for more than 10-15 minutes. PLEASE HELP!!!!!!
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