Looking for another set of eyes
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.
Blue- starter current
Red-intake pulses with pressure pulse sensor
Yellow-exhaust pulses with pressure pulse sensor
Green- #1 ignition sync
Hi Jonathan looks like you have a leak on number five intake
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
Mode 6 will show misfire counts better check again
Won't be live but should direct you to problem cylinder whether it's number 1 or 5
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
“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?
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
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.
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.
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
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…
Great job so what is the exhaust restriction? Lifter?
Have not taken apart yet but will post the find. Soon
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
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.
Thanks for posting this! Great case study. It was fun to see the culprit revealed in real time.