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Engine runs fine until warmed up then it backfires

Tiny
RANDALL1961
  • MEMBER
  • 1990 CHEVROLET SILVERADO
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 85,000 MILES
Engine runs fine until warmed up, about three miles, then it backfires on passenger back exhaust and slows down cannot accelerate, but will idle. I have replaced plugs cap and rotor, MAP, TPS, water temperature sending unit no positive result.
Saturday, January 14th, 2017 AT 9:23 AM

3 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Check for a vacuum leak under TBI unit may be the problem. Then scan for codes by crossing A and B b on ALDL. Also, check plug wires 5000 ohms per foot.
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Saturday, January 14th, 2017 AT 9:42 AM
Tiny
RANDALL1961
  • MEMBER
  • 2 POSTS
Have not replaced wires. Trying to avoid, but will and send you a reply as to results.
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Saturday, January 14th, 2017 AT 9:46 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,513 POSTS
Please let us know what happens so it will help others.

Best, Ken
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Wednesday, January 18th, 2017 AT 6:17 AM

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