Case Study XC90 misfire with Steve Smith Non-intrusive engine evaluation [Motor Age] 

Excellent the cylinder pressure graph showing the delay in valve opening/closing relative to the good cylinder makes me confident in narrowing down the issue down to a possible valvetrain issue on that cylinder within the initial golden hour of investigation & giving the customer a estimate to look at the camshaft & followers as a next step rather than doing the usual & saying it needs a head off mate. A win for the customer & freeing up time for other jobs avoiding unnecessary labour all with verifiable proof. 👍🏻

Great video. Lots of awesome information learned in a short amount of time. I love my PicoScope and my pressure tranducers but I always follow them up with a leak down test if I suspect a cylinder has a leakage issue. I bought extra male and female couplers (Foster series 2) for my WPS500x. This way I can unplug the pressure transducer and install my leak down tester right into the compression hose already in the cylinder. Only takes a minute then I know for sure if a valve is leaking or not and which one. I also have to disagree with the line of, "Diagnosing stops when dismantling starts." You came up with all kinds of awesome information to help the customer out but the car's not diagnosed fully yet. The next step is pulling the valve cover and that is still very much a part of the diagnostic process and very much a billable expense even if the customer decides to scrap the car! Information costs money. Thanks for the neat case studies!

Very good and well documented information to be presented to the customer. Thanks for sharing your insides in this particular case of study. Blessings

Nice case study Steve!

So good.

In cylinder pressure overlay can be misleading, because doesnt factor for crankshaft acceleration/deceleration. In fact maybe your good and bad cylinder have exactly the same valve opening and closing events. Why would a worn camshaft cause late closing of a valve? My guess out of experience with this engines is that the lower compression is caused by the piston not travelling all the way up in the bore, because of failed connecting rod bearing.