03 GMC Yukon P0300 misfire 5.3

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Doubeleive

Wes
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I figure a parts cannon would be costly and just replace parts I’d get lucky and all but at the result of it still misfiring is just a waste I’ll try to clean the maf sensor and get a new air filter see if it makes the truck run better if it still doesn’t then I’ll take it to a reputable shop to do live data check and see if it’s running well or not
random misfire can be hard to track down, if you have future plans to do repairs yourself then that parts cannon money is better spent on a scanner that can read live data as that can pay for it's self over time, versus having to pay a shop to do it.
even with a little cheap multimeter you can test some electrical parts, grounds and ohm's, etc
 
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Jeffs5-3

Jeffs5-3

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random misfire can be hard to track down, if you have future plans to do repairs yourself then that parts cannon money is better spent on a scanner that can read live data as that can pay for it's self over time, versus having to pay a shop to do it.
even with a little cheap multimeter you can test some electrical parts, grounds and ohm's, etc
Any good scanner you recommend that I can rock this isn’t the only Gm vehicle I have so it’s be nice to have it just in case and for more self diagnosis
 

Doubeleive

Wes
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Any good scanner you recommend that I can rock this isn’t the only Gm vehicle I have so it’s be nice to have it just in case and for more self diagnosis
well the tech2 is the go-to scanner for the gmt800-900 those run about $400 right now for a clone. but there are tons of others out there, I couldn't even start to say which one, some of the autels seem to be decent and do all brands but the prices and options are all over the chart.
if you search here on the forum there have been many threads on scanners and what they can and cannot do.
 
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Jeffs5-3

Jeffs5-3

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Current conditions of my air filter and my maf sensor
 

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Larryjb

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When I first got my '02 (used), I also had a random misfire. It turned out to be the intake manifold seal. This is very common in the 02-06, and perhaps beyond.

The seals get compressed and let in a ton of unmetered air, cuasing misfires. It was rather tough to diagnose it because you'd expect it to be lean with the unmetered air, but rich because of the unburned gasoline. However, I was lucky and the random misses were mostly one bank only, which ruled out everything before the intake manifold for me.
 
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Jeffs5-3

Jeffs5-3

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When I first got my '02 (used), I also had a random misfire. It turned out to be the intake manifold seal. This is very common in the 02-06, and perhaps beyond.

The seals get compressed and let in a ton of unmetered air, cuasing misfires. It was rather tough to diagnose it because you'd expect it to be lean with the unmetered air, but rich because of the unburned gasoline. However, I was lucky and the random misses were mostly one bank only, which ruled out everything before the intake manifold for me.
I have heard that this is a common issue I will definitely look into that as well also considering that this was one of the old spark plugs from the third cylinder on the driver side
 

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Fless

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I have heard that this is a common issue I will definitely look into that as well also considering that this was one of the old spark plugs from the third cylinder on the driver side

Wouldn't mind seeing that plug with a lighter background. Hard to see the tips.
 

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