Uploaded March 2026 | Updated September 2026, 3 weeks ago
2008 Chevy Avalanche with an idle-only misfire and a P0300 random misfire code. In this lesson, I use misfire counters and secondary ignition testing to isolate the dominant cylinder and prove the fault without guessing.
This is a great example of why a random misfire code does not mean every cylinder deserves equal attention. Cylinder 1 stood out immediately in the data, and the secondary ignition pattern supported that direction. The fault ended up being a bad spark plug with a cracked porcelain, and moving the plug moved the bad pattern and the miss.
In this video I cover:
• Using history and current misfire counters to choose direction
• Why one cylinder can cause a P0300
• Secondary ignition waveform analysis on a coil-over-plug system
• Burn time changes and what they can mean
• Why idle-only misfires often make you suspect a mechanical issue first
• Using a swap test to confirm the fault
• Why misfire counters help, but should not be blindly trusted
Timestamps:
Misfire counters and P0300 direction [00:00]
Cylinder 1 stands out in the data [00:27]
Idle-only misfire: initial diagnostic thoughts [01:04]
Secondary ignition setup and waveform review [01:17]
Cylinder 1 burn time inconsistency [02:18]
Comparing cylinder 1 to known good cylinders [03:31]
Mechanical suspicion vs ignition fault [04:26]
Spark plug inspection changes the direction [05:04]
Cracked porcelain found on cylinder 1 plug [05:20]
Swap test setup and verification [06:08]
Bad waveform moves with the spark plug [06:29]
Misfire counters after the plug swap [07:16]
Final diagnosis and repair recommendation [08:14]
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• In-depth classroom lectures straight from my book
• Exclusive case studies with live vehicles pulled into class
• Real-time troubleshooting using proven methods
• Ability to post help requests on our forum
• Fundamental training on automotive electrical & electronics diagnostics
📘 Want to learn more about diagnostics?
Check out my field manual Engine Performance Diagnostics, available as both an eBook and paperback:
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⚠️ Disclaimer:
ScannerDanner LLC is not responsible for misuse, unauthorized changes, or incorrect application of any information provided. Always follow proper safety protocols when using tools, equipment, or procedures discussed in this video. Use this content at your own risk.
#P0300 #MisfireDiagnosis #SecondaryIgnition
2008 Chevy Avalanche with an idle-only misfire and a P0300 random misfire code. In this lesson, I use misfire counters and secondary ignition testing to isolate the dominant cylinder and prove the fault without guessing.
This is a great example of why a random misfire code does not mean every cylinder deserves equal attention. Cylinder 1 stood out immediately in the data, and the secondary ignition pattern supported that direction. The fault ended up being a bad spark plug with a cracked porcelain, and moving the plug moved the bad pattern and the miss.
In this video I cover:
• Using history and current misfire counters to choose direction
• Why one cylinder can cause a P0300
• Secondary ignition waveform analysis on a coil-over-plug system
• Burn time changes and what they can mean
• Why idle-only misfires often make you suspect a mechanical issue first
• Using a swap test to confirm the fault
• Why misfire counters help, but should not be blindly trusted
Timestamps:
Misfire counters and P0300 direction [00:00]
Cylinder 1 stands out in the data [00:27]
Idle-only misfire: initial diagnostic thoughts [01:04]
Secondary ignition setup and waveform review [01:17]
Cylinder 1 burn time inconsistency [02:18]
Comparing cylinder 1 to known good cylinders [03:31]
Mechanical suspicion vs ignition fault [04:26]
Spark plug inspection changes the direction [05:04]
Cracked porcelain found on cylinder 1 plug [05:20]
Swap test setup and verification [06:08]
Bad waveform moves with the spark plug [06:29]
Misfire counters after the plug swap [07:16]
Final diagnosis and repair recommendation [08:14]
🔧 Looking for deeper training?
Join ScannerDanner Premium for next-level diagnostics training:
👉 Join Here – 14 Days for $1
scannerdanner.com/join-scannerdanner-premium.html
On ScannerDanner Premium, you’ll get:
• In-depth classroom lectures straight from my book
• Exclusive case studies with live vehicles pulled into class
• Real-time troubleshooting using proven methods
• Ability to post help requests on our forum
• Fundamental training on automotive electrical & electronics diagnostics
📘 Want to learn more about diagnostics?
Check out my field manual Engine Performance Diagnostics, available as both an eBook and paperback:
👉 https://linktr.ee/scannerdanner
🧰 ScannerDanner Tools:
https://linktr.ee/scannerdanner
⚠️ Disclaimer:
ScannerDanner LLC is not responsible for misuse, unauthorized changes, or incorrect application of any information provided. Always follow proper safety protocols when using tools, equipment, or procedures discussed in this video. Use this content at your own risk.
#P0300 #MisfireDiagnosis #SecondaryIgnition
![Why Wont This Jeep Start?? [Part 2]](https://i.ytimg.com/vi/Hjgs_8wX6Ks/mqdefault.jpg "Why Wont This Jeep Start?? [Part 2]
Here is the link to part 1 https://youtu.be/glYGv3CyVWU
Im sorry guys, I wasnt going to release this one until we had a true answer, but the customer is not returning emails or phone calls. From what I was told, it was taken to a dealer and the Jeep was confirmed to be running and back on the road. My friend Pete has tried to reach out to her multiple times, and I even emailed her personally, explaining the situation and she never got back to me either. I do not think she is angry with us as she wasnt even charged, so Im not sure why she wont communicate with us.
From your comments in part 1, here are two things that I would have tried:
1. leaving the battery disconnected and terminals jumped together overnight
2. disable the fuel pump, relieve system rest pressure through my fuel pressure gauge, clear the 3 flooded cylinders I can get to (again), then crank the engine over with no fuel pressure and bring fuel pressure back immediately if it fires up from residual fuel in the system
3. fool the ECM with engine temperature (alter the ECT signal) to where it thinks the engine is hot, to eliminate the cold start enrichment
The key with getting this to relearn, is to get the engine running. Alcohol % is calculated based off of the oxygen sensors and fuel trim after the PCM sees an increase in fuel level.
Im also not sure that the process I chose, with removing fuel, only to put that same fuel back in, was a good move as there was never any start-up period in between, which may have been needed.
Frustrated and disappointed would be how I feel about this one. If I ever get an update from this customer, I will post and pin the comment here.
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For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available at www.scannerdanner.com as an eBook or paper book.
Want even more diagnostic training? Whether you are a DIY trying to fix your own car, someone looking to become an auto technician, or a current auto technician that wants to get more into diagnostics, subscribe to ScannerDanner Premium https://www.scannerdanner.com/join-scannerdanner-premium.html There is a 14 day free trial.
On ScannerDanner Premium I will bring you right into my classroom at Rosedale Technical College. You will find page for page lectures taken right from my book as well as exclusive classroom type case studies. What is so special about these classroom case studies? I pull live problem vehicles directly into my classroom and we troubleshoot them in real time, using and applying the theory and testing procedures we learn during the classroom lectures. There is no better on-line training of how to troubleshoot automotive electrical and electronics systems anywhere!
Disclaimer:
Due to factors beyond the control of ScannerDanner LLC, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. ScannerDanner LLC assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. ScannerDanner LLC recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of ScannerDanner LLC, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not ScannerDanner LLC.")
![Quick message about my video editor [Caleb Danner]](https://i.ytimg.com/vi/JAnbqU7Em9E/mqdefault.jpg "Quick message about my video editor [Caleb Danner]
Just a quick video about my son Caleb and how proud I am of him! For those following our videos, he is the one that makes them so watchable even for those who have no idea what we are doing! Of course his humor comes into play at times too (like me riding a horse in our last video lol)
Love you my son. I couldnt do this without you.")
![Holley Terminator X Universal In Tank Fuel Pump Installation [78 Dodge Power Wagon]](https://i.ytimg.com/vi/JKOgIR9LrTE/mqdefault.jpg "Holley Terminator X Universal In Tank Fuel Pump Installation [78 Dodge Power Wagon]
This is a return type fuel system which was recommended over the return-less system as it helps to keep the throttle body cooler.
Holley Terminator X wiring diagram pdf
https://documents.holley.com/0e6992fcbea20610d28b5e03b0ba55e339d5323f.pdf
#holleyterminatorx
#holleyefi
#holleyperformance
@HolleyPerformance
@JAMSIONLINE
00:00 - intro
01:00 - picking the location
02:00 - cutting the tank
03:47 - adapting my float to the new pump assembly
05:47 - fuel tank supporting ring install
08:40 - installing the new pump assembly and fuel lines
12:38 - wiring the pump
20:34 - detailed wiring diagram of fuel pump relay
📘 Want to Learn More About Diagnostics?
Check out my field manual, Engine Performance Diagnostics, available as both an eBook and paperback at:
👉 https://linktr.ee/scannerdanner
🔧 Looking for Deeper Training?
Whether youre a DIYer, an aspiring tech, or a professional looking to sharpen your skills, join ScannerDanner Premium for next-level diagnostics training:
👉 Join Here – 14 Days for $1
https://www.scannerdanner.com/join-scannerdanner-premium.html
On ScannerDanner Premium, youll get:
*In-depth classroom lectures straight from my book
*Exclusive case studies with live vehicles pulled into class
*Real-time troubleshooting using proven methods
*Post help requests on our forum
*Fundamental training on diagnosing automotive electrical and electronics systems.
ScannerDanner Tools:
https://linktr.ee/scannerdanner
⚠️ Disclaimer:
ScannerDanner LLC is not responsible for misuse, unauthorized changes, or incorrect application of any information provided. Always follow proper safety protocols when using tools, equipment, or procedures discussed in this video. Use this content at your own risk.")
