Just a question since I have a little more information. Removed cat with no change so put in a new NTK upstream 02. This 3.9L magnum runs crummy for about 10 miles, it will stall, start right up and runs fine. Seems like it likes a red hot exhaust to really heat up the sensor but I thought the heater circuit would take care of that. Question being now should I use an OEM sensor from Dodge which I see is around $100.00 compared to the NTK which is around $60.00 and that is what I have in the truck now. Misfire codes random once in a while....no 02 codes though. I know the bosch sensors are not a good choice. I figure if this is so critical maybe it needs what was put in it originally? Thoughts are appreciated.

 

Did you replace with a wideband ? Go back to OEM, cures the problem!!

 

NTK or Denso was the OEM supplier, depending when it was built.

 

Built in 1998. I only see an improvement when the engine is run a long time. It's normal after that. I know the 02 sensor doesn't start to work till it reaches 600° or more. What exactly does the heater circuit do? Does it just heat it up enough to get it to work? Seems like the exhaust needs to be hotter or the sensor needs to work a lot faster.

 

The heater does just that, heats it so that it functions.

The upstream O2's monitor the fuel trim. The downstream monitors the catalyst efficiency.

You might want to put a scanner on it and get some live data. It may not be an 02 problem.

 

Yes, I have been doing just that....live graph to see what's going on. Looks like the data shows the o2 operating correctly, upstream. Getting used to the graph as to what it's suppose to look like. The voltage goes up and down like it is suppose too varying from .15 to .9 volts. Need though to compare graphs as to what it looks like when it runs perfect. It almost seems like it's getting a little better by only missing a short time now....maybe for 20 minutes of running then....absolutely nothing and idles great? Two independent PCM's do the same thing so I don't believe it's that unless they get better the hotter they get. Annoying and out of the box problem.