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Backfires

Tiny
STEVE BOOK
  • MEMBER
  • 1999 CHEVROLET BLAZER
  • 4.3L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 100,000 MILES
Truck backfires the PCV sometimes on starting, but
runs perfectly after resetting PCV cap.
Friday, November 18th, 2016 AT 10:48 AM

7 Replies

Tiny
JIS001
  • MECHANIC
  • 3,411 POSTS
Do you have the correct PCV valve installed? Also have you tried scanning for codes? I would use a more advance scanner for that rather then the quick small ones.
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Friday, November 18th, 2016 AT 11:01 AM
Tiny
STEVE BOOK
  • MEMBER
  • 4 POSTS
I have ordered the PCV valve. The only code that shows up is a knock sensor.
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Monday, November 21st, 2016 AT 7:36 AM
Tiny
JIS001
  • MECHANIC
  • 3,411 POSTS
Okay, replace the valve and reset the light and let us know if that fixed the problem or if the code returns.
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Monday, November 21st, 2016 AT 9:18 AM
Tiny
STEVE BOOK
  • MEMBER
  • 4 POSTS
Replaced the valve, the only code is a knock sensor, an if still backfired.
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Friday, November 25th, 2016 AT 7:38 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,690 POSTS
Hey Steve,

I backfire could be caused by an leaking intake valve, here is a guide that will explain all reasons for a backfire.

https://www.2carpros.com/articles/engine-backfires-while-running

Please run some tests and get back to us so we can continue helping you.

Best, Ken
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Saturday, November 26th, 2016 AT 7:14 PM
Tiny
STEVE BOOK
  • MEMBER
  • 4 POSTS
Does anyone know where the gulp valve is located on 1999 blazer?
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Wednesday, November 30th, 2016 AT 12:40 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,690 POSTS
If your engine has one it will be near the exhaust manifold on either side.
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Wednesday, November 30th, 2016 AT 8:28 PM

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