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GM YUKON: I HAVE A 2004 GMC YUKON AND I HAVE A P0300 CODE

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HI I HAVE A 2004...
HI I HAVE A 2004 GMC YUKON AND I HAVE A P0300 CODE AND I HAVE DONE A COMPLETE TUNE-UP AND I STILL HAVE THE SAME CODE, WHAT COULD BE THE PROBLEM?
Submitted: 1 year ago.Category: GM
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4/23/2016
GM Mechanic: GM Bob, ASE Certified Technician replied 1 year ago
GM Bob
GM Bob, ASE Certified Technician
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Satisfied Customers: 1,151
Experience: 30 plus years experience as GM technician, ASE Master Technician and GM Certified.
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Hello my name is ***** ***** I can help.Does your scan tool show misfire history or current misfire data? This would help narrow down which cylinder is missing. Do you feel the misfire?Have you check for spark?How does it run down the road?Sorry for so many questions Please get back with me Thank you
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Customer reply replied 1 year ago
I do have spark I feel the misfire when I'm driving and the check engine light flashes intermittently
GM Mechanic: GM Bob, ASE Certified Technician replied 1 year ago
Does it misfire at idle?Do you have a scan tool?Ha
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Customer reply replied 1 year ago
I believe so I a Snap On Soulus
GM Mechanic: GM Bob, ASE Certified Technician replied 1 year ago
Can you find the data list for misfire?It should show what cylinder is missing.
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Customer reply replied 1 year ago
It showing cylinder number seven and cylinder number two on the live data screen
GM Mechanic: GM Bob, ASE Certified Technician replied 1 year ago
which one is counting up faster?
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Customer reply replied 1 year ago
I am looking at a graph of line goes up and moving
GM Mechanic: GM Bob, ASE Certified Technician replied 1 year ago
Sometimes one cylinder will make another show a misfire
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Customer reply replied 1 year ago
How would you determine which one what information do I need
GM Mechanic: GM Bob, ASE Certified Technician replied 1 year ago
With a long screwdriver can you listen to each injector. When its running.Make sure 2 and 7 are clicking. Sound the same as a good cylinder
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Customer reply replied 1 year ago
It looks like cylinder seven is more sporadic all over the place
GM Mechanic: GM Bob, ASE Certified Technician replied 1 year ago
You could pull off a spark plug wire see if it misfire worse. If it don't that is the cylinder
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GM Mechanic: GM Bob, ASE Certified Technician replied 1 year ago
It was missing before the tune up?Yes it looks like 7
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GM Mechanic: GM Bob, ASE Certified Technician replied 1 year ago
How was the spark plug you took out?Any oil fouled
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Customer reply replied 1 year ago
Yes it was misfiring before the tune up so from the pictures you believe I should replace number seven and it should shouldn't need number two? No there was no oil
Customer reply replied 1 year ago
I also did a compression test compression was good
GM Mechanic: GM Bob, ASE Certified Technician replied 1 year ago
Is there any engine noise? ticking
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Customer reply replied 1 year ago
No
GM Mechanic: GM Bob, ASE Certified Technician replied 1 year ago
Was the compression the same as a good cylinder?
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Customer reply replied 1 year ago
Yes sir
GM Mechanic: GM Bob, ASE Certified Technician replied 1 year ago
Have you tried swapping coil and wire?See if it moves
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Customer reply replied 1 year ago
I have not I have 3 coils just in case should I replace the 2 cylinders misfiring ?
GM Mechanic: GM Bob, ASE Certified Technician replied 1 year ago
I would start with #7. It is the left side rear cylinder.Just making sure we are on the correct cylinder
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GM Mechanic: GM Bob, ASE Certified Technician replied 1 year ago
There is still chances you may have a bad injector.
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Customer reply replied 1 year ago
OK will do number seven left rear if you're sitting in the vehicle
GM Mechanic: GM Bob, ASE Certified Technician replied 1 year ago
correctAlso listen to the injector make sure its clicking loud like a good cylinder.Keep me postedThank you
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GM Mechanic: GM Bob, ASE Certified Technician replied 1 year ago
If it was a intake leak. You would have lean codes.
Also you would not feel it going down the roadHow did the injectors sound?
You could swap injectors see if it moves
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GM Mechanic: GM Bob, ASE Certified Technician replied 1 year ago
I have had catalytic convert cause misfire on one cylinder.
If you remove the front O2 sensor.
See it gone.
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Customer reply replied 1 year ago
So I am looking at the cylinder misfire data cylinder seven is at 22,31,45,55,65,72 then it goes back to 0 and keeps misfiring
Customer reply replied 1 year ago
After changing the intake manifold gasket now I have bank one PO 171 code system to lean any ideas
Customer reply replied 1 year ago
So now I have cleared the codes and only the PO 300 code comes back
GM Mechanic: GM Bob, ASE Certified Technician replied 1 year ago
The misfire counter goes to 100 and resets. This is normal.Did you do anything with the injector????
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GM Mechanic: GM Bob, ASE Certified Technician replied 1 year ago
Did the P0171 lean condition come back?
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GM Mechanic: GM Bob, ASE Certified Technician replied 1 year ago
Just checking to see how you are doing.
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Customer reply replied 1 year ago
Still have major misfire 7 maybe a cam bearing
GM Mechanic: GM Bob, ASE Certified Technician replied 1 year ago
Ok here is a check list. Let me know if you did it or not. Swapped coil and spark plug wire? Check new spark plug? See what it looks like after running with misfire? Compression test? Would like to see the results Swapped Injector or replaced? Removed front O2 sensor out of exhaust on left side? Test drove see if misfire is gone? Remover left valve cover look at rocker arms? See if they are moving same as the other cylinders. This engine will run with the coils off on one side. Please get back with me
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GM Bob
GM Bob
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