1987 CHEVY TRUCK SPARK KNOCK

  • Tiny
  • 87V20
  • 1987 Chevrolet Truck

Engine Performance problem
1987 Chevy Truck V8 Four Wheel Drive Automatic 10,000 miles

My 1987 V20 pickup with a 5.7 TBI engine has around 10,000 miles on a new long block. At part throttle under load it pings and smokes. I have replaced the O2 sensor, MAP sensor and have checked the EGR valve. The EGR valve works properly. I check the Vacum selenoid for the EGR valve and there seems to be no vacum there, but this may be due too not being fully up to temp. Would the knock sensor be the most likely culpret for this. It did have a 13 code, that is why I replaced the O2 swensor and it also indicates the MAP sensor. Really need some help here, thanks.

Friday, May 2nd, 2008 AT 9:53 AM

2 Answers

  • Tiny
  • rasmataz
  • Member

Recheck the ignition timing-The knock sensor might not be retarding the timing when it starts to detonate- also the double check the EGR valve-


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Friday, May 2nd, 2008 AT 10:31 AM
  • Tiny
  • pear69
  • Member

What is the compression ratioof the new long block? Check for vaccume leaks.

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Friday, May 9th, 2008 AT 6:09 AM

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