Everything is finally functional on my '03, D2, except the oxygen sensors. Just replaced both upstream sensors. Getting 9 codes. The D2 runs great until it heats up (10 miles of driving). Then I've got poor idling, poor acceleration, random shifting. I replaced both upstream 02 sensors because they were throwing codes (first the right, then the left).

Codes:
P0152 02 Sensor Circuit High Voltage
P0308 Cylinder 8 Misfire Detected
P0155 02 Sensor Heater Circuit
P0130 02 Sensor Circuit
P1300
P0306 Cylinder 6 Misfire Detected
P0302 Cylinder 2 Misfire Detected
P0135 02 Sensor Heater Circuit
P0304 Cylinder 4 Misfire Detected

Aside from buying premium 02 sensors (these were not), does anyone have ideas on what is forward from the upstream sensors that would be feeding them unburned fuel? MAF sensor?

Thank you for your help.

 

When you say these were not, I suspect this might be your underlying issue.

You need to buy Bosch 02 sensors. Any brand other than Bosch (and even sometimes the Bosch ones) tend to cause these issues.

Also, have you cleaned the MAF?

 

There are 4, the downstream/after cat O2's could be bad as well.
And +1 on the Bosch brand only. Everything I read, and everyone I talk to says the same. Lots of stories of non Bosch O2's causing problems.

 

Bosch = bad, at least as far as O2 sensors go. There are lots of threads on this forum where people have repeatedly encountered Bosch O2 sensors that are bad out of the box.
Walker sensors seem to be the way to go for reliability. I have them on my truck right now.

 

Thanks for posting this.
I found all 4 Walker O2's for $259, free shipping, 1 year warranty, and price match guarantee.
That beats the heck outta $400+ for 4 Bosch.
As I near the end of my rebuild, I have wanted to replace all 4 O2's, so I know what I have, fresh start, etc.
I really didn't want to spend over $400, but, $259 is still alot of money, but is alot more reasonble.
I'm going to get a set.
Thank you!

 

Seconding the Walker sensors. I've had no issues out of them, unlike the Bosch. 2 crib deaths out of 2 sensors I bought. The previous two only lasted 2 years.

 

Please share the link or vendor for the Walker O2 deal.

 

I will be the alternative voice here. I have 5 current Disco's (wifes, mine, daughters, off-road), so it makes it easy for me swap and troubleshot sensors, including MAF and 02.

I typically go to the u-pull-it junkyard every weekend. I have started using nothing but used OEM 4 wire 02's from low mile cars in good shape. I can usually tell when I take them out if they were any good, because they are almost white. Almost all downstream sensors are good because they almost never see excess fuel or coolant (Cat burns it off).

With an Elm327 bluetooth OBD reader and the torque android app you can read the almost realtime data off of the O2's. They should cycle regularly. You can disconnect the MAF and the O2's will still cycle if they are working. You can open a propane torch in to MAF and the 02's shoudl go rich (.9 v) if they were stuck lean. If you pull a vacuum line loose, they should go lean (.1v)if they are stuck rich. If they are faulty, they fail open (0v).

On cold start O2's should be slightly rich, and then start cycling. If they start lean and stay lean they are bad. If you get the torque app you can record the data and post it up, we can help troubleshoot from there.

 

Here is what some lightly challenging Googling has found.
* Walker makes two kinds of O2 sensors. One is "Standard", the other "Premium".
* In most cases the "Premium" level is about 20% more.
* Best price I could find for the "Premium" sensors was on Amazon.
* Upstream Premium, $40.35 each. Walker 350-34462
* Downstream Premium, $43.94 each. Walker 350-34188

Net/net to replace all four O2 sensors - $157.10

 

I too like to take my pampered children to experience the Post-Armagedon look and feel of an old-school junkyard. Unfortunately not enough D2 parts cars around Austin, TX to pick-a-part. What I can add in the "Too Rich/Too Lean" vein ... I was getting a "Too Lean" code before I changed out the left side O2 sensor. Now that's gone, but this new "Heater" code is popping up. Never seen that before.