Misfire cylinder three and code P0303

Tiny
JCANIZZO8
  • MEMBER
  • 2002 CHEVROLET S-10
  • 4.3L
  • 6 CYL
  • 4WD
  • MANUAL
  • 136,000 MILES
Changed plugs, cap and rotor and new distributor. Truck starts but still has miss in cylinder three. Coil changed, no change in misfire. Lean code p0303 still persists. Pulled number 3 spark plug wire off distributor, no change in engine. I popped the fuel rail and got good fuel pressure. Engine starts fine and has no power, just a misfire that I cannot find source of. No vacuum leaks. Like I said, pull number 3 wire and no change in engine. It is not getting spark only on that cylinder. Is it cam position or crank position sensor, PCM?
Sunday, December 29th, 2019 AT 10:44 AM

5 Replies

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

Did you check the compression on that cylinder? I would start there.

https://www.2carpros.com/articles/how-to-test-engine-compression

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

Roy
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Sunday, December 29th, 2019 AT 11:44 AM
Tiny
JCANIZZO8
  • MEMBER
  • 3 POSTS
Yes, is at 75 psi.
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Sunday, December 29th, 2019 AT 4:46 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Okay. That is the issue. You need at least 140 to 160. That is why you have the misfire.

Roy
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+1
Sunday, December 29th, 2019 AT 5:00 PM
Tiny
JCANIZZO8
  • MEMBER
  • 3 POSTS
Thanks.
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Sunday, December 29th, 2019 AT 7:44 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
You are welcome.

Always glad to help.

Roy
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Monday, December 30th, 2019 AT 4:46 AM

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