A carbon study

Craig Technical Support Specialist Chicago, Illinois Posted   Latest  
Case Study
Driveability
Education
2014 GMC Terrain Denali 3.6L (3 LFX Flex) 6-spd (6T70)
Intermittent Low Power Complaint No Codes

Customer complained of an occasional low power event we were unable to duplicate ourselves. Vehicle has no codes and approximately 75,000 miles of mixed city and highway use. Being a GDI injected engine intake valve deposits were suspected. A bore scope was snaked through the intake and valves inspected confirming our suspicions. Photos are from cylinders 4 and 6 intake valves. As we are all aware this is becoming a large issue and I decided to inspect the engines ability to breath pre and post repair, the more data the better. I used 2 Autoditex pressure pulse sensors one in the intake and one in the exhaust with a sync to cylinder # 2. The first pattern shows large jagged intake pulls and a horrible exhaust pattern, the valves were cleaned using chemical soak and manual scraping. The second waveform shows the results, I was quite amazed at the differences having a lower amplitude intake signal and a much greater exhaust amplitude which required raising the exhaust signal voltage on the scope to keep the pattern on screen, both patterns look much more uniform after service with the exhaust pattern showing a significant change.

My theory is the amplitude change in the intake is due to less air velocity on the intake pull with clean valves, and with more air in cylinder the exhaust push should be greater, and we find a higher exhaust amplitude as suspected. I am hoping to publish more of these carbon studies, perhaps a user group could be formed to gather pre and post cleaning captures providing us all with a usable dirty valve database. 

All thoughts and comments appreciated.

Craig … 

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Chris Diagnostician
Bryans Road, Maryland
Chris Default
 

Nice work! That looks like a big difference between the two.

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Edward Owner
San Antonio, Texas
Edward Default
 

Yup I see this all the time on gm and ford GDI we tried BG products, GM top cleaner, what I found that works the best is a carbon blaster tool from ESC BMW and mini dealerships use the same tool. Auto tool makes a carbon blaster tool that won't break the bank. Great post

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Craig Technical Support Specialist
Chicago, Illinois
Craig Default
 

Thanks for information, we are presently considering the BMW walnut blaster ourselves.

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Michael Technician
Amherst, Massachusetts
Michael Default
 

Hello Edward Leon, Where did you get the ESC tool and what is the approximate cost? How did you adapt the tool intended for a BMW on a GM vehicle?

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Edward Owner
San Antonio, Texas
Edward Default
 

Hello Michael I bought tool about 3 years ago and that was the only one on the market today we have several of them. I recommend a aftermarket Autool or harbor freight, at the time i used rubber hose and tape to seal off the ports, once you understand the concept in the sequence pretty straight forward. Today there's different adapters you could use ports adapters make your own but the whole…

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Craig Technical Support Specialist
Chicago, Illinois
Craig Default
   

Good evening Edward where did you source the intake port adapters from? I have been looking for something right along those lines. Craig

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Edward Owner
San Antonio, Texas
Edward Default
 

Craig unfortunately Craig I did not source these adapter just giving an example from eBay I just use the old hose instead. But the answer to your question is you can source them off eBay as long as you know the port sizes

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Craig Technical Support Specialist
Chicago, Illinois
Craig Default
 

That works sir, thank you.

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Edward Owner
San Antonio, Texas
Edward Default
 

Happy to help

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David Diagnostician
Philadelphia, Pennsylvania
David Default
 

Great case study Craig

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Caleb Diagnostician
Mishawaka, Indiana
Caleb Default
 

So cool man. Haven't had the chance to use pressure pulse sensors for carbon. Awesome to see it being done!!

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Craig Technical Support Specialist
Chicago, Illinois
Craig Default
 

Presently have another of the same vehicle in now only a 4 cylinder, pulled a breathing test on it last week intake looked rough exhaust looked good. Just performed a sea foam intake service to it as a product test, post clean results will be performed later this afternoon, it will be interesting to see if any noticeable change occurs.

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Edward Owner
San Antonio, Texas
Edward Default
 

Craig Be careful has some these cleaners can cause large chunks of carbon deposit to break off and damage the catalytic converter, here are some photos of Ford Eco-boost Walnut Carbon blasting after just three minutes it removed most of the carbon

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Matthew Technician
Elmsdale, Nova Scotia
Matthew Default
 

Very cool to see the waveforms to go along with this issue.

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