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Vehicle Information: I own a 2006 Dodge Durango Limited with the standard 4.7 V8. The car has 154k miles.

About Me: I am fairly self-reliant with repairing cars. I am, however, not great at diagnostic work. Although, this is something that I am learning with every project. I share this with the community because I am no car repair expert; I am simply good at following instructions. Any advice on the below issue would be appreciate.

Background: About a month ago, the car developed a weird idle, which felt like a periodic and random stumble. I attempted to address the issue by replacing the spark plugs. In the process, I followed the standard protocols for adding diaelectric grease to the coil pack boots. The issue did not improve. I took the car to Firestone, and they completed the diagnostic test. As a remedy, they recommend new oxygen sensors, battery, and purge valve solenoid. All four o2 sensors were replaced along with the battery and purge valve. The periodic stumble continued; however, new codes emerged: P0300 and P0303. The car was running terrible at this point. P0303 isolated an issue on the third cylinder. I identified and replaced a cracked coil pack. I also took the opportunity to clean the intake manifold. Due to error on my part, I had to replace the idle air control valve and the throttle position sensor. (Long story...please don’t ask why.) Subsequently, the P0303 code disappeared and the car started running better as long as the car was warm. The original stumble has been resolved.

Current Issue: Here is the current issue that I cannot seem to resolved. The car has a rough idle at startup, but once warm, it runs beautifully. Startup is no challenge for the car. Computer still shows code P0300, which refers to multiple misfires. The local auto parts store recommends that I replace the remaining (7 total) coils packs. My questions:
  • Should I replace all of the coil packs? Or, should I test and identify the problem coil packs?
  • Would the EGR valve have anything to do with this issue?
  • Any recommendations?
 

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Welcome to Allpar. A cold misfire could be spark plugs.
Are they the correct Champion RC12MCC4 Copper Plus?

Any sign of water getting into the spark plug tubes, like corrosion? There was a TSB # 18-024-06 for a new cowl weather strip to keep water from dumping on top of the engine from rains or car washes. Described here:
Coil-on-Plug Ignition: The Art of COP Misfire Diagnosis - Automotive Service Professional (at https://www.autoserviceprofessional.com/article/97278/coil-on-plug-ignition-the-art-of-cop-misfire-diagnosis )
 

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Discussion Starter #3
Welcome to Allpar. A cold misfire could be spark plugs.
Are they the correct Champion RC12MCC4 Copper Plus?

Any sign of water getting into the spark plug tubes, like corrosion? There was a TSB # 18-024-06 for a new cowl weather strip to keep water from dumping on top of the engine from rains or car washes. Described here:
Coil-on-Plug Ignition: The Art of COP Misfire Diagnosis - Automotive Service Professional (at https://www.autoserviceprofessional.com/article/97278/coil-on-plug-ignition-the-art-of-cop-misfire-diagnosis )
Yes, I purchased the correct spark plugs from Autozone.

There is no wetness on the engine or in the spark plug tubes. There was a brow, rust-like residue in cylinder #7. Would this be water corrosion?
 

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A small vacuum leak would cause roughness when cold. The extra air would lean out the a/f mix and a cold motor is more sensitive of the a/f mix. When warm, the motor is much more tolerant of a slightly lean a/f mix.

The erg valve could be a possible source. If the valve is not fully closing it would lean out the a/f mix. It is still operating well enough to fully open properly and not trigger an egr code though.
 

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Discussion Starter #5
A small vacuum leak would cause roughness when cold. The extra air would lean out the a/f mix and a cold motor is more sensitive of the a/f mix. When warm, the motor is much more tolerant of a slightly lean a/f mix.

The erg valve could be a possible source. If the valve is not fully closing it would lean out the a/f mix. It is still operating well enough to fully open properly and not trigger an egr code though.
Thanks. I will look into the EGR valve.
 

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Discussion Starter #6
I am also receiving guidance from a user on another forum that the coolant temperature sensor maybe to blame. Does anyone concur with this suggestion?
 

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I am also receiving guidance from a user on another forum that the coolant temperature sensor maybe to blame. Does anyone concur with this suggestion?
I think that's a fantastic suggestion! :D
 

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. . .

Current Issue: Here is the current issue that I cannot seem to resolved. The car has a rough idle at startup, but once warm, it runs beautifully. Startup is no challenge for the car. Computer still shows code P0300, which refers to multiple misfires. The local auto parts store recommends that I replace the remaining (7 total) coils packs. My questions:
  • Should I replace all of the coil packs? Or, should I test and identify the problem coil packs?
  • Would the EGR valve have anything to do with this issue?
  • Any recommendations?
. . .
Cylinder misfire can be caused by deficiencies in spark plug wire, coil, spark plugs. Also misfire can be caused by an extremely lean air - fuel mixture on one or more cylinders. I would NOT replace anymore parts.

You need to use a scan tool and look at the short term, long term fuel trim values and the upstream oxygen sensor values for bank 1 and bank 2. At cold start the oxygen sensors need to warm up before functioning. Once the oxygen sensors start reporting valid values, the engine management system goes into closed loop operation. The oxygen sensors should report almost identical values and should oscillate with a value less that 0.45 volts (lean condition and a value greater that 0.45 volts (rich condition). Likewise the short term fuel trim should oscillate from a small negative % to a small positive % value. Fuel trim values stuck with a large negative value (less than -10%) or a large positive value (greater than +10%) are and indication of a fuel delivery problem with one or more injectors.
 

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I have seen connector corrosion at the engine coolant temperature sensor. The resistance told the PCM that the engine was at -40°F without setting a fault code because the temperature value was still a 'believable' value to the PCM. Use a scan tool to watch values when cold.
If the linear EGR valve has a metal exhaust inlet tube going to it, feel it right after start-up to see if it is getting warm, indicating flow when there should be none. Use caution as these can get hot in a hurry if there is an EGR flow present.
While in open loop (cold) operation, the O2 sensor signals aren't used. Always diagnose first.
 

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Discussion Starter #10
Thank you, everyone. I just purchased a BlueDriver OBD2 scammer. I will check the EGR, ECT, o2 sensors as recommended.
 

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Folks, the scanner showed an issue with the bank 1 upstream o2 sensor. See attached image. I am going to replace and warranty that sensor. My guess is that if the ECT was not working then the the bank 2 upstream sensor would give an inappropriate reading as well. I will update everyone when I exchange this sensor.
9880B060-269F-435E-A13C-F41D1094A2E9.jpeg
 

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OEM O2 sensors may be an important consideration. I have had issues with Bosch and 'universal' sensors, although there are those who have not had issues. The electrical characteristics may fall outside the planned threshold which will affect some, but not all applications.
A discussion here:
Are Bosch o2 sensors really this bad? (at https://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1997647 )
The O2 sensors are not used when first started while the engine is still cold, only when it enters closed loop (feedback) operation.
 

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I second the go with OEM sensors, my 2005 T&C drove me crazy over O2 sensors, Be sure to look and see if there is any note about the emission label PN, that is what bit me on the T&C (FWIW, I used to own a carburetor and ignition shop and was pretty familiar with the oncoming FBC and EFI stuff). I sold the shop but kept a lot on equipment and currently have a Snap-On Solus Pro.

As far as when the O2 sensors come on-line, my F350 converted to a 1996 OBD-II compliant EFI system will start controlling the mixture in less than 2 mins of running. If I have the battery or the EEC keep alive power disconnected, it will go so lean on a cold start due to loss of adaptive memory it will barely keep running. Once you get everything working correctly, you may need to do a "hard reset" on the PCM to clear the adaptive memory, then give it a few days to re-learn things. A check with your BlueDriver on the OBD-II readiness monitor will confirm when it is finished the re-learn time. Until it shows "ready" it is still "tweaking".
 
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Folks, the scanner showed an issue with the bank 1 upstream o2 sensor. See attached image. . . . . .
I agree with your assessment. From the text that is displayed bank 2 upstream O2 indicates 0.645 volts: rich condition. If the air - fuel mixture is reported rich to the PCM (powertrain control module) you would expect the short term fuel trim for bank 2 to be less than 0.0% (take away fuel). And the short term fuel trim bank 2 displays -3.9% which indicates taking away fuel. That is correct.

Bank 1 upstream O2 sensor indicates 0.135 volts: lean condition. This gets reported to the PCM and you would expect the short term fuel trim for bank 1 to be greater than 0.0% (add fuel). But the short term fuel trim bank 1 is -3.1% which is taking away fuel. This is inconsistent and not correct.

What is most important is to see how the oxygen sensors work in unison and the short term fuel trims react to a positive signal or negative signal from the oxygen sensors. When the oxygen sensors report rich air - fuel mixture the short term fuel trims should be negative and when the oxygen sensors report lean air - fuel mixture the short term fuel trims should be positive. Is this happening consistently over 20 - 30 second intervals?

I would suggest swapping the location of bank 1 and bank 2 upstream sensors and see if the pattern switches locations as witnessed by the meter. If this happens then you know which O2 sensor is faulty.
 

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Discussion Starter #17
I replace the current Bosch bank 1 upstream o2 sensor with a new version of th same. Attached is the scanner output. On initial crank, the car was smooth and ran beautifully down the road with no codes. I shutoff the car, allowed it to cool, and re-cranked it. Scanner showed three pending codes: P1128, P0135, and P0161.
  • What are you seeing?
  • Recommendations on next steps?
07159F04-E0E4-4A27-A927-3D324D500072.jpeg
 

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I replace the current Bosch bank 1 upstream o2 sensor with a new version of th same. Attached is the scanner output. On initial crank, the car was smooth and ran beautifully down the road with no codes. I shutoff the car, allowed it to cool, and re-cranked it. Scanner showed three pending codes: P1128, P0135, and P0161.
  • What are you seeing?
  • Recommendations on next steps?
Go back and review the Y T video posted by Gerry G (post #14). The technician in the video outlines why you should NOT use Bosch oxygen sensors on a Chrysler vehicle. You need to replace the Bosch sensor with OEM or an aftermarket sensor that is Chrysler compatible. Obviously the Firestone store had NO CLUE about this problem and sold you something just to make money!

Replace with appropriate oxygen sensors, clear codes and test again. I bet your problems will disappear.
 

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On my 2008 4.7 NTK as the OEM supplier. I just put new NTK sensors in my Dakota.
 
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