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Hi everyone, new to the site but not new to ScannerDanner. Been watching his videos for a while now and recently got the book. I'm looking forward to going premium and working through it.
I got a BlueDriver scanner and every time we go on a drive (I make my wife drive now) I plug it in and watch the live data just to learn. I saw something that didn't make sense, but maybe you guys can help me out.
First the car: 2005 Ford Freestar SEL, 4.2 L, ~145,000 miles. All stock, no mods.
When we're at cruising speed (~45-55 mph) I was looking at engine load, RPM and throttle position. When it's coasting, I saw the RPMs on the scanner jump to around 4000, while the tachometer stayed constant at ~1600 and the engine seemed normal. Sometimes the RPM jump would be very short, sometimes it would be for several seconds. I attached a pdf of the data, and highlighted the areas where the jumps happened. It's a long file but you don't have to go very far to find the jumps highlighted. Sorry I don't have any more data points but that is what I was looking at.
So I have the live data (I assume from the crank sensor) showing me these 4000 RPM spikes, while the engine and the tach seem steady at 1600 the whole time. I wouldn't know that there was an issue if I weren't seeing the live data. On a side note, I also looked at the Mode 6 data (love the BlueDriver) and it was giving me a PID (?) that I looked up and found it was "potential misfire data as reported by the crank sensor". Related?
Is this normal? Or is it a problem? I'm still learning so any help or explanation would be appreciated!
I would bet that this is a issue with blue driver lag I've only seen glitches like this on cheap scanners I wouldn't get hung up on it if your not having an issue it is possible for your ckp to be causing this but not likely as you would probably be having other issues as well and they usually drop out rather than spike upwards
I had the very same issue, but all my data maxed out for 0.40Ms and went back to normal,
I looked at my time stamp and it showed that
Say @ 2.40.040 it happened but before that time it was 2.40.090 so it jumped back a ms and in turn glitched the data ,
So check your time right down to the ms and you may see a time jump.
The following user(s) said Thank You: scottberggren
Hey scottberggren! Thanks for posting your data - BIG glitch around 390 seconds. :blink:
I'm with Ben and Lee, very likely to be a scanner issue. No way the crank sensor could be glitching out that badly and not create a perceptible driveability problem.
Is the BlueDriver similar to other ELM327 scanners? If so, it might be fun to try another phone app and see if the problem is still there. Might help to distinguish between a hardware and software problem. :huh:
The following user(s) said Thank You: scottberggren
Thanks for the ideas. I figured it might just be a scanner relic and not anything major. If the engine was actually jumping from 1600 to 4000 (in overdrive, think of that gear ratio...) I would definitely have noticed something.
As another thought, how is that scanned RPM signal generated? It must be different from the signal sent to the tachometer. I know the crank sensor measures revolutions of the crank, right? Could it be measuring blips that happen as the transmission "coasts"? I may be way off but it only happens at cruising speeds (never at acceleration) and I wondered if it was picking up from the transmission rather than the engine. Just a thought, but I may be way off. I just got my Freestar workshop service manuals in the mail today so I'll need to look it up. If I find anything interesting that might shed some light on this I'll share.
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