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Discussion Starter #1
Hey guys and gals, I started a discussion a while back about my 98 Dakota having bucking, sputtering, backfiring, stalling problems. OBD scanners say I have a faulty O2 sensor (upstream). I don't believe the O2 sensor itself is the problem. The truck seems to be running lean, has low power when climbing, and is suffering a major efficiency drop. I've read that so many things can cause the trouble I'm having till I just don't know where to start. I recently replaced the ignition coil which inadvertently seems to be adding to my problems. Any advice will help, and if you've already responded to my other post, I apologise but this my only vehicle and I need to get it running.
 

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1988 Dodge Dakota LWB RC 3.9V6 3 speed auto
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Well, you KNOW the O2 is bad, which is used to dial in the air/fuel mixture.

Tackle that first.

Adage - if you know A is bad, and it can cause the symptoms, fix A, then worry about anything ELSE that can cause the symptoms. If A is bad, you won't fix it even if it's actually due to B ...

RwP
 

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C'mon Dodge - NEW DAKOTA
2003 Dakota Club Cab Sport 4.7L
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What leads you to believe it's NOT bad? Those are all symptoms of a bad O2 sensor.
 

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Discussion Starter #4
What leads you to believe it's NOT bad? Those are all symptoms of a bad O2 sensor.
Well I have an exhaust leak at the donut ring, and I believe that also causes a lean condition. I can't say for certain what the problem actually is.
 

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1988 Dodge Dakota LWB RC 3.9V6 3 speed auto
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facepalms

Yes, it can.

Because it adds air to the stream the O2 is reading.

But the mixture is actually RICH.

Fix that, replace the O2, and then troubleshoot.

Or don't.

But geez louise ....

RwP
 

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C'mon Dodge - NEW DAKOTA
2003 Dakota Club Cab Sport 4.7L
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Well I have an exhaust leak at the donut ring, and I believe that also causes a lean condition. I can't say for certain what the problem actually is.
No, you can't. Until you fix the known problems.
Both the leak and the O2 sensor will cause the computer to mis-adjust your mixture, run your engine in the wrong portion of the calibration curve. Get it?
 
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Discussion Starter #7
No, you can't. Until you fix the known problems.
Both the leak and the O2 sensor will cause the computer to mis-adjust your mixture, run your engine in the wrong portion of the calibration curve. Get it?
I went by the local Dodge house today and the parts specialist told me that they did not have a flange gasket for my exhaust. He told me that the manifold is tapered one way and the exhaust pipe is tapered the other way so that they fit together thus eliminating the need for a gasket. As far as the air fuel ratio goes I pulled two spark plugs out of my motor (the first one on each bank) and neither one looks excessively rich or excessively lean. This one's really got me scratching my head, but the only thing I know to do right now and I'm going to go ahead and change the O2 sensor this weekend and hope for the best.
 

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C'mon Dodge - NEW DAKOTA
2003 Dakota Club Cab Sport 4.7L
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Excellent decision. How many miles on the truck? O2 sensors last from 90k to maybe 150K, they get "lazy" and still work but the data the ECM sees is faulty, causing it to make faulty decisions.
 

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C'mon Dodge - NEW DAKOTA
2003 Dakota Club Cab Sport 4.7L
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I'm at 155K.

I can tell mine are due too, the truck is lacking mid range torque, fuel economy has dropped. It's all very gradual because that's how O2 sensors degrade.

Please post again after you replace your sensors (and I did use the plural form there). I'm anxious to hear the outcome. You will need to drive and let the ECM re-learn the sensor response.
 

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Discussion Starter #11
I'm at 155K.

I can tell mine are due too, the truck is lacking mid range torque, fuel economy has dropped. It's all very gradual because that's how O2 sensors degrade.

Please post again after you replace your sensors (and I did use the plural form there). I'm anxious to hear the outcome. You will need to drive and let the ECM re-learn the sensor response.
I took the truck to O'Reilly for another scan before changing the O2 sensor. The OBDII showed me a shortlist of codes P0300, 0301, 0303, 0305 0351, 0420, and 0132. They suggested that I remove the catalytic converter, because it's likely clogged.
 

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I recently had similar drivability issues with my 98 3.9L Dakota at 136K miles. Finally got so bad that it set several cylinder mis-fire codes and P0132 code (O2 Sensor High Volts Bank 1 Sensor 1). Your upstream (before catalytic converter) oxygen sensor is probably failed. The vehicle runs fine cold because it is running in "open loop". When warm, the vehicle changes to "closed loop" control, which uses input from the upstream O2 sensor to control engine fueling. On my scan tool I could see the upstream O2 sensor latched at false full rich (1.0 volt). Then I saw the fuel trims trying to lean out the fueling, which is why the vehicle sputters and backfires when warm. It is literally not getting enough fuel to run properly and make power.

I installed a new upstream O2 sensor, purchased from the local dealer (they are still available thru Mopar). My Dakota runs perfectly now. On my scan tool all is normal now. The O2 sensor voltage switches low and high, which is proper behavior.

Note there are several videos on the internet on how to change an oxygen sensor. I used a map gas torch to heat the bung on the exhaust y-pipe. Then the old oxygen sensor came out easily. I did however use a really good oxygen sensor socket to break it loose (6 point Lisle oxygen sensor socket). Write to tell us if a new upstream O2 sensor fixed your vehicle too
 

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Hey guys and gals, I started a discussion a while back about my 98 Dakota having bucking, sputtering, backfiring, stalling problems. OBD scanners say I have a faulty O2 sensor (upstream). I don't believe the O2 sensor itself is the problem. The truck seems to be running lean, has low power when climbing, and is suffering a major efficiency drop. I've read that so many things can cause the trouble I'm having till I just don't know where to start. I recently replaced the ignition coil which inadvertently seems to be adding to my problems. Any advice will help, and if you've already responded to my other post, I apologise but this my only vehicle and I need to get it running.
I had the same problem with my 2000 durango, I chased that for a month, replace both your O2 sensors. With bad O2 your computer does not know if the fuel ratio is right. I replaced both and it fixed the problem.
 
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