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2007 Limited 5.7 QD-II
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Discussion Starter · #1 ·
I've got a 2007 Commander Limited 5.7 with just over 100,000 miles. Every time the under-hood/intake air temperature is over 130 F it starts "bucking" and throws a P0300 code. I reset it and it comes back as soon as the temp. gets above 130 F. Runs great at all other times. I've replaced the intake air temp sensor, air filter, camshaft sensor, MAP sensor. Also, I'm using the Superchip Flashpaq for Jeep MDS disable feature and 87 octane tune.
Any ideas about what could be the issue?
 

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2006 5.7 4x4 Limited
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50 Posts
Since P0300 is random cylinders misfiring, it sounds like the computer is adjusting fuel/air/spark based on the 130 F reading. Have you tried disabling the MDS disable, and see if it changes the bucking at 130 F ?
Or disabling the 87 octane fuel tune?
 

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2007 Limited 5.7 QD-II
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Discussion Starter · #3 ·
Hi Rxfire;
Yes, I've tried pretty much everything; return to stock setting, 91 Octane tune, etc. the bucking, P0300 code still occurs.
Possibly an ECM issue at higher temps?
 

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Dallas TX
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112 Posts
May want to go back through the items you have changed already and hit them with some contact cleaner and dielectric grease, just to be sure all is good-n-tight. may want to do the same at the PCM with the "big" connection blocks. did you change plugs/coil packs recently? any clues that preceded the code?
 

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Discussion Starter · #5 ·
May want to go back through the items you have changed already and hit them with some contact cleaner and dielectric grease, just to be sure all is good-n-tight. may want to do the same at the PCM with the "big" connection blocks. did you change plugs/coil packs recently? any clues that preceded the code?
I'll definitely try some contact cleaner and dielectric grease. Any tips on removing the "big" connection blocks?
Changed the plugs/coil packs about 3000 miles ago.
As soon as the "bucking" starts, I get the code.
 

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2006 Commander Limited, 5.7 Hemi QD2
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@DLSander , please make a signature with the details of your commander. It is tough to help if we always have to go back many posts to tell what engine you are talking about.

Since I figured out you have the Hemi, what spark plugs did you put in, the Hemi likes the stock Champion coppers, others can cause problems.
 
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@DLSander I picked up a few cans of the quick dry cleaner and dielectric grease at Home Depot. I go through a bunch as I will clean the area around the plugs before I started unplugging things. Like most of the larger plugs there is a slide release then push and they pop out actually pretty easily.
video that may help
 

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I've got a 2007 Commander Limited 5.7 with just over 100,000 miles. Every time the under-hood/intake air temperature is over 130 F it starts "bucking" and throws a P0300 code. I reset it and it comes back as soon as the temp. gets above 130 F. Runs great at all other times. I've replaced the intake air temp sensor, air filter, camshaft sensor, MAP sensor. Also, I'm using the Superchip Flashpaq for Jeep MDS disable feature and 87 octane tune.
Any ideas about what could be the issue?
@DLSander ;

This may help you;

OBD-II Check Engine Light Trouble Codes (obd-codes.com)

OBD-II Trouble Code: P0300 Random/Multiple Cylinder Misfire Detected (obd-codes.com)

P0300 Random Misfire Detected Code

This diagnostic trouble code (DTC) is a generic powertrain code. It is considered generic because it applies to all makes and models of vehicles (1996-newer), although specific repair steps may be slightly different depending on the model. So this engine code article applies to Chevrolet, Ford, Nissan, Toyota, Dodge, Honda, GMC, etc.

Basically this P0300 code means that the the car's computer has detected that not all of the engine's cylinders are firing properly.

A P0300 diagnostic code indicates a random or multiple misfire. If the last digit is a number other than zero, it corresponds to the cylinder number that is misfiring. A P0302 code, for example, would tell you cylinder number two is misfiring. Unfortunately, a P0300 doesn't tell you specifically which cylinder(s) is/are mis-firing, nor why.

Symptoms
Symptoms may include:
  • the engine may be harder to start
  • the engine may stumble / stumble, and/or hesitate
  • other symptoms may also be present
Causes
A code P0300 may mean that one or more of the following has happened:
  • Faulty spark plugs or wires
  • Faulty coil (pack)
  • Faulty oxygen sensor(s)
  • Faulty fuel injector(s)
  • Burned exhaust valve
  • Faulty catalytic converter(s)
  • Stuck/blocked/leaking EGR valve / passages
  • Faulty camshaft position sensor
  • Defective computer
Possible Solutions
If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.

If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.

Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open.

It is helpful to have access to a factory service manual and an advanced scan tool to properly diagnose a random misfire DTC.

 

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Discussion Starter · #9 ·
@DLSander , please make a signature with the details of your commander. It is tough to help if we always have to go back many posts to tell what engine you are talking about.

Since I figured out you have the Hemi, what spark plugs did you put in, the Hemi likes the stock Champion coppers, others can cause problems.
@DLSander , please make a signature with the details of your commander. It is tough to help if we always have to go back many posts to tell what engine you are talking about.

Since I figured out you have the Hemi, what spark plugs did you put in, the Hemi likes the stock Champion coppers, others can cause problems.
Added some info to my signature, thanks for the advice.
Plugs are Champion, I believe the # is RE14MCC4
 

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2006 Commander Limited, 5.7 Hemi QD2
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Thank you for the signature, Yes you used the correct plugs.:D
 

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2007 Limited 5.7 QD-II
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Discussion Starter · #12 ·

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Here's what's shown in my signature:
2007 Limited 5.7 QD-II
I assumed that if I listed QD-II, it's obviously a 4X4.
I hate to break it to you @DLSander , but, that's not what's in your signature.

If that was there, I wouldn't have asked you.

I'll fix it for you when I get back home on Monday.
 

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2006 Commander Limited, 5.7 Hemi QD2
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I changed his signature Big Blue, added QDII.
Was
2007 XKJP74 LIMITED, EZB - 5.7L HEMI MULTI DISPLACEMENT ENGINE, DGE - 5-SPEED AUTOMATIC TRANSMISSION, MINERAL GRAY MET. CLEAR COAT
Now
2007 XKJP74 LIMITED, EZB - 5.7L HEMI MULTI DISPLACEMENT ENGINE, QDII, DGE - 5-SPEED AUTOMATIC TRANSMISSION, MINERAL GRAY MET. CLEAR COAT
 

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I changed his signature Big Blue, added QDII.
Was
2007 XKJP74 LIMITED, EZB - 5.7L HEMI MULTI DISPLACEMENT ENGINE, DGE - 5-SPEED AUTOMATIC TRANSMISSION, MINERAL GRAY MET. CLEAR COAT
Now
2007 XKJP74 LIMITED, EZB - 5.7L HEMI MULTI DISPLACEMENT ENGINE, QDII, DGE - 5-SPEED AUTOMATIC TRANSMISSION, MINERAL GRAY MET. CLEAR COAT
Thanks @rblapham ;
 

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Hi Rxfire;
Yes, I've tried pretty much everything; return to stock setting, 91 Octane tune, etc. the bucking, P0300 code still occurs.
Possibly an ECM issue at higher temps?
I had so many drivability issues with many codes. I replaced sensors, plugs, coil packs & it still gave me fits. I realized the problem worsen as temps grew warmer. Finally, I ordered a rebuilt pcm & to my amazement, It fixed my issue(s).
 

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