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Megasquirt 5100 RPM shut-off

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Old Jun 20, 2006 | 02:45 PM
  #1  
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5100 RPM shut-off

Well, my car ran fine for about 100 miles or so, then it started randomly hesitating at 5100 RPM, the tach would drop to 0 and then instantly bounce back up. I hooked up my laptop and watched while driving, and it seems the MS shuts off at 5100 and instantly boots back up and resumes driving. I messed with some settings, (mainly rev-limiter/launch control) and suddenly it worked fine again. I tried driving it the next day, and the same hesitation happened. I varied the amount of throttle but it still happened.

Finally I downshifted and got the revs above 5100 and it was fine, as long as it didn't drop below that it was smooth. Then, as I was driving to the store, I bounced it off this and the idle took a dive and would dip below 400, accelerating was rough, and it sounded different. After I was done at the store, I went to start it up and it ran fine with idle where it was supposed to be, and acceleration was normal, except until the magic number.

So what I was wondering is, is there a bug in the code or what? I've tried using both 029Q and 029Q2, but the same thing happens.

Last edited by papiogxl; Jun 20, 2006 at 03:07 PM.
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Old Jun 20, 2006 | 03:20 PM
  #2  
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I forget, Are you using 2nd trigger or missing tooth?
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Old Jun 20, 2006 | 04:23 PM
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I'm using missing tooth. Thanks Ken.
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Old Jun 20, 2006 | 04:41 PM
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Which wheel decoder scheme are you using? 025 style has been reported to cuase issues for some. Switching to the alternate, 024s9, may solve the issue.
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Old Jun 20, 2006 | 04:44 PM
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024s9, its really strange, the MS just turns off then back on at 5100 RPM
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Old Jun 20, 2006 | 05:09 PM
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this sounds like it might be an electrical issue... I'd go over the wiring looking for anything that could be cutting power to the MS...

What do you mean it "turns off and then back on?"

You mean it completely loses power, or the CPU resets or...?
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Old Jun 20, 2006 | 09:35 PM
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The MS resets itself at 5100 RPM, above that its fine, below that its fine. I tried jiggling the harness while it was on, but it did nothing. Its odd that it started behaving this way on its own, without any changes being made between when it started and stopped. The only thing I coould think of was when it stopped, it was cool out. This is kind of frustrating because I want to take it to the track Friday to see the difference, but I'm losing my useable power.
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Old Jun 20, 2006 | 10:15 PM
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Why don`t you try reflashing the firmware and reinstalling the .msq to see if that corrects it.
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Old Jun 21, 2006 | 10:20 AM
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if it only does it when it's hot outside then I'd say you have wiring problems somewhere. Without seeing your wiring harness I can't really help more than that.

There isn't anything in software that'll completely reset the CPU at a certain rpm...
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Old Jun 23, 2006 | 11:03 PM
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It seems to be load dependant, which is odd. I've tried checking the harness and reloading the software. Also just recently it started doing this over random large bumps, but not all of them. It is not heat related, as I figured out. Could it possibly be the crystal on the MS board? I have a glob of silicon there to hold it.
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Old Jun 24, 2006 | 10:45 AM
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I mean it could be ANYTHING that's not quite secure or isn't soldered or connected right...
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