Before we continue Antonio, could you confirm the capture provided looks at exhaust tailpipe pulsations and referenced to cylinder 1?
I ask because there are no Channel labels and your pressure transducer appears set to Range 2 +- 1.4 bar.
If this is exhaust gas pulsations then could you take a look here viewtopic.php?p=103106#p103106
I would be happy to follow up on your capture “Renault_Clio_2008_Petrol_20220512-0001” as soon as you can confirm the signals on channels A and B
I have used the ignition event of cylinder 1 + approx. 10° as our TDC reference point (0 .. 720°)
See below: I have assumed a firing order of 1342
Uniformity and repetition are the ultimate goal when looking for anomalies in such waveforms and there are a couple of items highlighted above that we need to investigate
Above I have used the Pressure Waveform Overlay from Microsoft to help with identification of events in neighboring cylinders
I think we can agree that the intake “pull” for each cylinder occurs at the same point for all cylinders suggesting that the “full” closure of the exhaust valve and “full” opening of the inlet valve appear “on time” (approx. 30° after TDC on the respective exhaust stroke)
There appears to be a lot of turbulence/disturbance during the intake pull for cylinder 1 which I have highlighted with a large blue rectangle (again, compare this intake pull with neighboring cylinders)
This intake pull appears “stepped” in nature suggesting a change in cylinder volume (e.g. leak) or piston speed
Note how the commencement of the intake pulls for cylinder 1 and 4 are lower than cylinders 2 and 3 (highlighted with small blue rectangles)
Note also how the commencement of Cylinder 4 intake pull appears to be missing the defined double peak we see on the remaining cylinders suggesting a differing intake pressure during valve overlap
Could I ask what are the customer symptoms and how do these results compare with additional tests? (i.e., exhaust gas pulsations, 4-Gas analysis, crankcase pressure and DTC’s)
Please remember, this test is just one piece of the diagnostic puzzle and you have highlighted areas of concern
I would like to repeat this test when cranking from cold and again cranking from hot as valve clearances come into play here (especially with the missing double peak of cylinder 4 intake pull)
Using the cranking only test will also remove variables such as EGR if applicable to this vehicle?
If the vehicle uses LPG I would most certainly take a close look at exhaust valve clearances
I hope this helps, take care……Steve