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Cylinder misfire

Tiny
CHIPTHEMUNK
  • MEMBER
  • 2001 CHEVROLET ASTRO
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 200,220 MILES
First off. New cap, rotor, wires, plugs, and compression checks out. Now, my question is a bit of an odd ball. The misfire is constant. But if I use the computer to manually fire the injectors it starts working fine, no misfires at all. But after starting the van up again the misfire returns. Any ideas about why it would behave this way?
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Tuesday, February 5th, 2019 AT 5:36 PM

3 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good evening,

If you are manually commanding the injector on, then you are manually grounding the return line from the injector to the PCM.

That would indicate a possible bad PCM as that controls the operation of all injectors.

Roy
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Tuesday, February 5th, 2019 AT 5:48 PM
Tiny
CHIPTHEMUNK
  • MEMBER
  • 2 POSTS
This is a great suggestion. However, everything else runs great, just this one cylinder is misfiring. So I have to assume the PCM is fine. Could there be an exposed wire somewhere or ungrounded line? And does this matter? Sounds like I will be needing to replace the spider anyway.
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Wednesday, February 6th, 2019 AT 12:05 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
I agree. I would replace it. Very common failure.

Roy
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Wednesday, February 6th, 2019 AT 12:30 AM

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