Autonerdz forums

Here are a couple of fls captures on an 04 f 150 5.4 with a vct system. This engine is very sick and surprisingly only one cylinder has no compression according to a relative compression test and it's not where you might think it would be looking at the fls wave forms.  One of these captures is in the intake at about 510 rpm and the other is in the exhaust at about 1760 rpm. See if they will tell you anything about the condition of this motor or is there any useful info there at all.  I will add these in psdata so you can manipulate them and they were done on version 6.06 if it matters.
    Here is one from the exhaust.

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Hi Michael
     I agree those captures are hard to make much of. You may well be right about that exhaust valve leak at the fourth  in the order . I'll check that before it's gets torn down. The firing order here is 13726548.  I can't really slow the engine down and get a more stable capture over a longer period of time. If I let it idle  that wave as you call it running through the wave form will get like the intake capture and I'll have to raise the voltage scale on the scope to the point that you'll no longer see any individual pulses or it will run right off the screen.  It becomes extremely unstable at slower speeds. Did you look at the intake capture and notice how the wave running through the wave form is like the inverse of what you see in the exhaust?  I'm pretty much thinking about what I might see in these wave forms when the valve timing is way out of sync with the piston position.  The only thing that makes me rethink that  is the ignition and injector timing is right according to the crank sensor and the fact that I show eight cylinders in a relative compression test. I think if one cam was 360 out of time I would only see four  cylinders in a relative compression test. The cams are synced together so if one is out of time both are out of time. There was the possibility of one being 360 off but the eight pulses in the compression test kind of ruled that out I think. I can pretty positively say at least one intake valve is wide open or close to it when the piston comes to tdc compression. From the fls wave forms  it looks to be the 4th in the firing order but from the relative compression capture it would logically be the 7th in the firing order.
    Thanks for taking a look at that and giving me your opinion on what you see in there. I know it takes a bit of your time to look through those captures and annotate them as you've done. I know I spend a bit of time looking through them a number of times after I've looked through them the first time for anything that just obviously stands out. I notice it looks like you figure there is a pretty good delay in the fls reporting when compared to an electrical signal. I found about a 3 ms delay in my pv 500 but I've never checked the fls for delay. I have gone under the assumption that it was at least quite a bit faster than my pv 500  and haven't figured on the delay much when looking at these wave forms.  I believe it's a piezo device rather than a pressure transducer and assumed it to be faster to report. Do you figure the delay to be about the same as your pressure transducer? I guess I should check it and find out what the delay actually is so I can figure that in there as well.
 Here is a relative compression capture  to give you a little more info about why those fls waves may look like they do with the blue being starter current and the red being #1 primary.

A lot of the time (always) mechanical integrity is easier to see with the engine cranking and not running.
I use two FLS 100 testers and do intake and exhaust at the same time with a sync.
That way you don't have to deal with any turbulance caused by the misfire.
That is my 2 cents
Take it for what it is worth
Here is an example of a toyota

Wilf

Hi Michael
      I will get those wave forms but I got side tracked yesterday with Dogs and didn't get them done. Friend of mine was running a bear south of here for the game and fish folks with my tracking collars on his dogs. I have my name ph number and address on my tracking collars so all day long I kept getting calls about lost dogs showing up in folks yards. Most folks don't understand those collars are radio transmitters so they don't know what to think when you tell them that the dogs owner will be along shortly. I ended up taking a trip south to help round up dogs. In the old days these dogs had good homing instincts because they always just ran loose on a fellas property and went where they wanted but these days they spend all their time in a kennel so on a hunt after a couple days on track they get hungry and go to the first sign of civilization rather than home. The homing instinct has been kind of bred out of them so to speak.

     I see you and I are roughly on the same page with those wave forms. I came up with the peak in that intake wave being at about 442 degrees after #1 firing event but I also came up with 442 degrees after the firing event in the exhaust wave as being about 42ms after the firing event  you show that point as being a little earlier than 442 degrees. I still tend to think there is a valve timing problem here as well. I guess we'll know more about that as soon as I get those captures done.
     Time wise what do you figure the delay to be with the fls?  Thats something I'm still unsure of.