Carbon study 2

Craig Technical Support Specialist Chicago, Illinois Posted   Latest  
Case Study
Education
2012 GMC Terrain SLE 2.4L (K LEA Gas) 6-spd (6T45)
Fls Carbon Test

Vehicle came in for VVT solenoid codes on Saturday during the look over I decided to look again for possible carbon issues, vehicle has 67,000 miles and a neglected service history to put it politely. Intake valve cleaning performed with an intake fogging device, VVT solenoids changed, oil change and crankcase flush along with new plugs completed today's service. Pre carbon cleaning shows more jagged edges in the intake strokes, as well as a movement of jagged edges from the sides of the pulses to being at the top and bottom compared to post cleaning. Also noticed as during the last post a change in signal amplitude, with the intake pattern losing amplitude and the exhaust gaining. Unfortunately no visual inspection can be readily done, so pattern analysis is the only data at the moment. 

Please excuse the color swap from now on all intakes will be blue and exhaust in red.

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Interesting
Ray Diagnostician
North York, Ontario
Ray Default
 

Thank you for the Case Study.

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Interesting
Tom Owner/Technician
Boise, Idaho
Tom Default
 

Thank You . Great info . I was always scepticle of any benefit but my mind is changed....

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Anthony Technical Support Specialist
Kirkwood, Pennsylvania
Anthony Default
 

Hi Craig: I wish that you had the coil on the second capture. In your first post, it appears that there was a shift. I was curious to see if it happened here. Guido

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Craig Technical Support Specialist
Chicago, Illinois
Craig Default
   

Unfortunately the vehicle was needed by the customer, had to just grab the intake and exhaust, actually these are really the ones I want to focus upon, I am hoping to find commonalities in pre and post repair patterns to be comfortable enough in the data to call a vehicle clean or dirty as it were. I have noticed a decrease in amplitude on the intakes which I think comes from less resistance to…

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Anthony Technical Support Specialist
Kirkwood, Pennsylvania
Anthony Default
 

Hi Craig: It is the exhaust shift that jumped out at me. It could be nothing worthwhile but I'm a curious critter. Thanks for the response. Guido

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Rob Diagnostician
Bountiful, Utah
Rob Default
 

Were these captures taken with the engine running or cranking?

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Craig Technical Support Specialist
Chicago, Illinois
Craig Default
 

Running at idle, sorry should have mentioned that.

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Jose Technician
Woodland, California
Jose Default
   

Thanks for the waveforms Craig. I've been walnut shell blasting with great success. I use a borescope camera to confirm the vehicle needs service. The customer complaint that you get when this is a problem is " vehicle runs poor, misfires on cold start up" after a few minutes it runs s fine". Look for codes and you may have a P0300 with coolant temp and ambient or intake air temp being very…

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Craig Technical Support Specialist
Chicago, Illinois
Craig Default
   

Thanks for the feedback, we have used multiple methods of cleaning and inspection as well. The goal here is not to discuss how to clean the valves, but rather can someone gauge build up severity by using these patterns. I am aware of all the usual symptoms that lead to the carbon diagnosis, I am just wanting to see if there's perhaps a better way to quickly determine that conclusion as not every…

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Agree
Jose Technician
Woodland, California
Jose Default
   

Thanks Craig, I like your idea. I will start taking waveforms pre and post repair and see if we can find a pattern like you suggest. Very interesting stuff.

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Craig Technical Support Specialist
Chicago, Illinois
Craig Default
 

Thanks again Jose any additional patterns to analyze will be off great help hope to see some files soon. Craig

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Alex Technician
Denver, Colorado
Alex Default
   

I'd be interested to see if there was any improvement in manifold vacuum at idle after the cleaning. That's something that could be displayed on the scope with a pressure transducer. Since the change would likely be minimal, but still something that could be presented to the customer so they feel their money was well spent.

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Craig Technical Support Specialist
Chicago, Illinois
Craig Default
 

Thanks for the input Alex, definitely doable it would be interesting to see the differences especially on a newer design low vacuum motor. I know the WPS500 can do the test unfortunately all you get is a flat line, perhaps the old analog gauge will give a better looking indicator of improvement.

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Michael Technician
Amherst, Massachusetts
Michael Default
 

Hello Craig, Where did you put the carbon cleaning solvent on that engine and what was the product used? Did you have to dribble the chemical in over an extended period of time like an hour perhaps?

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Craig Technical Support Specialist
Chicago, Illinois
Craig Default
 

Hello Michael, this particular vehicle was cleaned using an aerosol can product from sea-foam, a representative from the company dropped off a sample and we decided to test it on this vehicle. It was sprayed into the the body with the engine running over a period of about 15 minutes. It's not the greatest design as you're stuck holding the sprayer button down until the can is emptied.

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