BACK FIRE AND CYLINDER MISFIRE

  • Tiny
  • Schirico
  • 2007 DODGE RAM
  • 90,000 MILES

2007 hemi pick up. I keep having a back fire. One tech said it's a miss fire on cylinder 6&7. I changed all 16 plugs. Still problem. Changed coils on 6, 7&8. Changed the cam or crank sensor (the one right below the alternator). Still having problems. No codes are being thrown on the computer. Help please

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Friday, December 30th, 2011 AT 4:28 AM

8 Replies

  • Tiny
  • Fixitmr
  • MEMBER

Is the backfire intake or exhaust?

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Friday, December 30th, 2011 AT 6:15 AM
  • Tiny
  • Schirico
  • MEMBER

Exhaust

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Saturday, December 31st, 2011 AT 4:58 AM
  • Tiny
  • Fixitmr
  • MEMBER

Backfire thru exhaust confirms misfire. So how did old plugs look? Especially 6-7. And does your motor have MDS?

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Saturday, December 31st, 2011 AT 7:15 AM
  • Tiny
  • Fixitmr
  • MEMBER

You could try switching injectors on 6-7 with nextdoor cylinders and see if problem moves with them?

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Saturday, December 31st, 2011 AT 7:17 AM
  • Tiny
  • Schirico
  • MEMBER

The old plugs looked good. Don't know what MDS means. Do injectors get bad or do the clog up.

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Saturday, December 31st, 2011 AT 2:56 PM
  • Tiny
  • Fixitmr
  • MEMBER

MDS is gas saving 4cyl operation when cruisin. Injectors do both.

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Sunday, January 1st, 2012 AT 5:59 AM
  • Tiny
  • Schirico
  • MEMBER

Yes. And I notice the backfire when I let off the gas pedal

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Sunday, January 1st, 2012 AT 11:04 PM
  • Tiny
  • Fixitmr
  • MEMBER

I would say MDS takes this diagnosis beyond do it yourself. VVT adds extra complications to any attemp to guess at fix. You will have to take it in to get diagnosed with the right equipment and procedures.

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Monday, January 2nd, 2012 AT 4:39 AM

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