Looking for another set of eyes

Jonathan Technician Nova Scotia Posted   Latest  
Discussion
Driveability
2015 Ram 1500 Express 3.6L (G ERB) 8-spd (845RE)
MIL Flashing
Engine Tick

Hello, looking for opinions on what appears to be going on in the this waveform picture​.​We have an idea of what we think is going on bu looking for more experienced opinions. II will upload a pico file tomorrow if time allows.

Thanks

Blue- starter current

Red-intake pulses with pressure pulse sensor

Yellow-exhaust pulses with pressure pulse sensor

Green- #1 ignition sync

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George Diagnostician
British Columbia
George Default
 

Hi Jonathan looks like you have a leak on number five intake

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George Diagnostician
British Columbia
George Default
 

Which cylinder misfiring is setting the check engine light I would go in to mode 6 to watch running misfires to see which one is counting

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Jürgen Owner
Mexico
Jürgen Default
 

Mode 6 won't show "live" misfires.

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George Diagnostician
British Columbia
George Default
 

Mode 6 will show misfire counts better check again

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George Diagnostician
British Columbia
George Default
 

Won't be live but should direct you to problem cylinder whether it's number 1 or 5

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Jeff Diagnostician
California
Jeff Default
   

I thought a leaking #5 intake valve but you would think #5 compression would be lower , I'm wondering with the ticking noise if theres a bad #1 intake rocker bearing that causing the #1 intake valve to open a bit early catching some of the exhaust pulse onto the intake

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Dmitriy Analyst
Ontario
Dmitriy Default
   

“I thought a leaking #5 intake valve but you would think #5 compression would be lower”. Very good point. And I would imagine that only a violent event can make the pulse sensor in the intake oscillate like that. What could it be?

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Ray Diagnostician
Ontario
Ray Default
 

If an exhaust valve is not opening during the exhaust stroke, when the cylinder's intake valve opens, the exhaust pressure will escape into the intake manifold

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James Instructor
Quebec
James Default
 

Compression on number 4 seems higher, Is number 1 exhaust valve closing early causing an extra pressure rise. What cylinder is coding? You have to love pressure wave forms often makes it so obvious you are dealing with a mechanical issue. In this case the engine tick also helps, but you do not always have a noise. To me in cylinder pressure would be the next step.

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Ray Diagnostician
Ontario
Ray Default
 

Cylinder 4 repeatedly shows higher starter amp draw than the other cylinders. Do an in cylinder cranking, running compression in cylinder 4. Or pull the valve covers, crank the engine and compare the high and low movements of the rockers.

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James Instructor
Quebec
James Default
 

Think you need to do a running compression cylinder on cylinder #1 as it is on exhaust stroke at same time as cylinder 4 is on compression

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Jonathan Technician
Nova Scotia
Jonathan Default
 

Ok so a little more details, this truck came in with a lack of power and the engine light flashing . we are new to this so we are trying to use some modern methods. ie scope stuff / no code diagnostics. our first step was take a relative compression with amp clamp. We did notice a higher hump / one that stood out , cool . so we added a sync which was number 1 coil . that lead us to number 4…

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James Instructor
Quebec
James Default
 

Great job so what is the exhaust restriction? Lifter?

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Jonathan Technician
Nova Scotia
Jonathan Default
 

Have not taken apart yet but will post the find. Soon

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Ray Diagnostician
Ontario
Ray Default
 

This is a GIF of the second PSD file. The exhaust valve did not open during the exhaust stroke, so the cylinder created maximum compression

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Jonathan Technician
Nova Scotia
Jonathan Default
 

Just took the valve cover off to find this. The cam lobs are worn round on number 1 exhaust All other cam lobs look un damaged.

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Leo Technician
New York
Leo Default
 

Thanks for posting this! Great case study. It was fun to see the culprit revealed in real time.

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Dmitriy Analyst
Ontario
Dmitriy Default
 

I am somewhat surprised that all this extra compression would only somewhat increase the compression peak on the relative compression trace rather than double it...

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