I need someone with alot of experience and troubleshooting knowledge with O2 sensors.

I have been trying to figure out why my MPG is so crappy on my 5.9 even with all the tuneups and upgrades to the engine to make it run smoother.

I started looking at the exhaust side to make sure my cat does not have any blockage but did not have a way to know if my O2 sensors is on the fritz.

I know that some sensors on our Durango will go bad, but not bad enough where it will throw a code. (TPS, speed, transmission sensors for example).

I bought a bluetooth ODBII module and Torque on my android phone. And it had the ability to test the O2 sensors. Great app. I can see if there are any error codes and clear them if needed.

From the look of the chart, one of my O2 sensors is flat lining when it is suppose to have a wavey line. I have posted the screenshot from my android phone using Torque to show you what I am talking about. One O2 sensor is behaving normally, the other O2 sensor is flat lining. However, I do not know which of these O2 sensors is the front or back sensor in relation to the cat.

These readouts are the same for both sensors if you are idling, or driving on the hwy.

I want to confirm from someone if the sensor that is flatlining is indeed defective so I can get it replaced and hope to bring my mpg back up a little.

If it needs to be replaced, I think I remember someone posting in this forum that they recommend OEM O2 sensors for best reliability and compatibility.

https://plus.google.com/u/0/photos?t...40219524154450

https://plus.google.com/u/0/photos?t...40221749061010

 

Both of your links are asking me to sign into google. Try posting a picture through photobucket or something similar.

 

i also have torque app, on mine O2 1x1 is pre-cat and O2 1x2 is post cat, if you want i can go out and hook it up to get you a graph screenshot

 

Define crappy mileage?

Mine gets 12ish or less for a decade+. This isn't broken, it is normal.

If I were giving one word guesses: "plenum"

IndyDurango

 

the way i found out mine were bad was to take em off. i found out that mine were melted and my cat had also partially melted on the inside. and yes i agree with indy, you should check your plemun gasket, remove your throttle body and check for oil in the bottom of your intaka manifold and black deposits like the oil cooked to the bottom of your intake manifold. and my d also gets around 8-12 city and 12-18 highway, depending on how heavy your foot is. lol.

 

Upon review of his sig, he has a "F1 Airgap Intake." I know a traditional M1 eliminates the plenum, I have no idea on that intake. It isn't the most common setup.

IndyD

 

For those of us that never seen one:



Yeah, i would say the Plenum is covered.....

 

I have a F1 airgap so no worries about plenum gasket and throttle bodies. TB is super clean as I keep my engine super clean and well maintained.

Indy - My MPG used to be 12-13 avg city/hwy. now it is 10-11 avg and sometimes drop below 10.

Here is another link to access my photos from google plus. Let me know if it requires a login. Should not require login as google picasa is now part of google plus.

https://plus.google.com/photos/11369...40220693043617

Sharp, so you are saying my post cat O2 sensor is bad then. That would suck. I had the back O2 sensor replaced a couple years ago. I will get it replaced with oem this time.

Damn, these sensors on these durangos are tricky bastards then. That's the third type of sensor on my vehicle to go bad, but not bad enough to throw a code to let me know. TPS and MAF sensor were the other two that went bad but not bad enough to throw a code.

Another question then. Would a bad or clog cat cause the post O2 sensor to flatline? Will need to take my vehicle to a muffler shop to confirm.


I will get that replaced and double check the pre O2 sensor again with another tool to confirm if it is good or not.

 

The Torque app for android is one of the best tools to have for your Durango or any modern vehicle. It can tell you the codes and even clear them.

The app itself I think is less than $10 bucks to get the full unlocked version. And buy a cheapo bluetooth OBDII device to hook up to your car for Torque to communicate with from Amazon for around $13 and you have a tool under $25 that can scan and diagnostics for your vehicle.

 

Worth every penny spent. I also bought their Hughes SCT tuner to tune the PCM for this intake and I have more midband power with this intake over stock. Definitely can feel the difference when you punch the pedal on the hwy.