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2001 6.8 Misfire

 
  #16  
Old 07-07-2019, 10:04 AM
DarkyDizzle13
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Originally Posted by Sam I Am View Post
Set your meter to AC and check right at the alternator, ground to case and test big output wire.
If you get an AC reading, it is a sine of a failing alternator.


 
  #17  
Old 07-07-2019, 10:35 AM
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Well, DANG - that's a lot, if that says 30 volts.

Anyone else able to do a quick check on their V10? I'd do it with my '97 Cougar (same alternator as my '01 V10), but my daughter has it right now.

Originally Posted by Sam I Am View Post
Set your meter to AC and check right at the alternator, ground to case and test big output wire.
If you get an AC reading, it is a sine of a failing alternator.
You too punny
 
  #18  
Old 07-07-2019, 10:54 AM
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Im hoping somebody comes back with some light here lol I'll buy an alternator right now if its possibly the problem.
 
  #19  
Old 07-07-2019, 11:20 AM
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Originally Posted by Krewat View Post
Well, DANG - that's a lot, if that says 30 volts.

From what i've just been reading that doesnt seem to be far from where it should be. Which means another idea shot down......sigh
 
  #20  
Old 07-07-2019, 11:32 AM
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The idea with alternators is, they have a diode matrix in them that only puts out DC voltage - it's pulsed, but still DC. And they generally peak around 15 volts. If you're getting 30 volts AC at the output, that means at least one of the diodes is shorted, and the voltage is swinging into the negative. Peak-to-peak on an AC waveform would give you around 30 volts.

I think the alternator is bad, but I just wanted someone else to check their alternator before we go spending your money
 
  #21  
Old 07-07-2019, 11:41 AM
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Originally Posted by Krewat View Post
but I just wanted someone else to check their alternator before we go spending your money
That is greatly appreciated lol But yes id love some more input on this.
 
  #22  
Old 07-07-2019, 12:31 PM
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Do you have any other vehicles around you could do the same check on? I'm worried your DVM might be giving out weird numbers. Can you turn off "auto" range?
 
  #23  
Old 07-07-2019, 12:36 PM
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Originally Posted by Krewat View Post
Do you have any other vehicles around you could do the same check on? I'm worried your DVM might be giving out weird numbers. Can you turn off "auto" range?
I'll check out my dmax and my wifes exploder when I get back home.

**dmax reads 29.4, so I assume the alt is good**
 
  #24  
Old 07-08-2019, 05:40 AM
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if you have an old analog voltmeter might be interesting to compare readings
 
  #25  
Old 07-08-2019, 07:40 AM
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So yeah, now we're back to checking COPs for arcing (or lack thereof).
 
  #26  
Old 07-08-2019, 07:42 AM
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I have a new set of coils I could throw in. Problem is if it runs good I still wont know if it's fixed. I have a camping trip in August and this pig needs to get there on all 10 cylinders.
 
  #27  
Old 07-08-2019, 07:49 AM
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I recall you changed the plugs already? What brand did you use?
 
  #28  
Old 07-08-2019, 07:54 AM
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They were autolites. Good ones I cant remember the name off hand.
 
  #29  
Old 07-08-2019, 03:23 PM
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Well new DMM shows 0.000v now. So I guess I can rule out the alternator.

As for the plugs they are Autolite Iridium XP.



 
  #30  
Old 07-08-2019, 03:31 PM
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I'm of the opinion that one of those coils is not firing right (or maybe more than one), and the unreleased energy is feeding back into the system. I remember at last a handful of people that reported OSS/VSS errors, and misfires, and the ultimate solution was at least one coil was doing something funky.

If you have them already, it can't hurt to put them in. Make sure you use dielectric grease around the tip of the boot where it meets the insulator of the plug, and where the boot seals on the coil.
 

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