2002 Chevrolet Express engine misfire

Tiny
SONYA JENSEN
  • MEMBER
  • 2002 CHEVROLET EXPRESS
  • 5.7L
  • V8
  • 2WD
  • AUTOMATIC
  • 237,000 MILES
I replaced engine with a 95000 mile used engine. After replacing engine there is a misfire at mid throttle. Engine runs great at idle and high throttle. I replaced spark plugs and wires, cap and rotor with no change. I have good compression on all cylinders. I tried using the new"used" fuel injectors also called the spider and still no change. I changed the throttle body today because of excessive wear and still no change. Im at a standstill, truck runs good, I dont feel the miss only going on scanner reads and check engine light blinking. Dont know what to try next. Any help would be appreciated!
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Thursday, August 13th, 2015 AT 7:47 PM

5 Replies

Tiny
WRENCHTECH
  • EXPERT
What are the exact code numbers being stored?
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Friday, August 14th, 2015 AT 5:53 AM
Tiny
SONYA JENSEN
  • MEMBER
It has a PO300 code. Random misfire. I cleared the codes and misfired at mid throttle again, cylinder 4 and 7.
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Monday, August 17th, 2015 AT 6:35 AM
Tiny
WRENCHTECH
  • EXPERT
What is the fuel pressure?
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Monday, August 17th, 2015 AT 6:37 AM
Tiny
SONYA JENSEN
  • MEMBER
I have 53 at idle 52 while revving it
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Monday, August 17th, 2015 AT 7:24 AM
Tiny
WRENCHTECH
  • EXPERT
There is your problem. The spec for this engine is 60-66PSI and it is very fussy about that. They usually won't even run under 55PSI.
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Monday, August 17th, 2015 AT 7:44 AM

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