Backfires through the exhaust

Tiny
DLBLAIR
  • MEMBER
  • 1997 GMC SIERRA
Engine Performance problem V8 Four Wheel Drive Automatic 200000 miles

My Z71 is backfiring through the exhaust and missing at mid range RPM. I have changed the plugs, wires, cap and rotor also cleaned the EGR system and installed a new temp switch all with no results. There is a 20 amp fuse in the box under the hood that is listed as Engine that blows every-time I put a new one in - could that be related to the problem? Anyone know what that fuse goes to? It is not a ECM fuse.
Thanks for any help you can give!
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Sunday, March 1st, 2009 AT 8:43 PM

3 Replies

Tiny
OBXAUTOMEDIC
  • EXPERT
Hello,

Check out this guide

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

Here is what someone said

Locate the crankshaft timing marks, most engines timing marks are at the front of the engine on the harmonic balancer. Near the balancer there is a small pointer or scale to align the balancer mark too. When the engine is running this gauge or pointer should align with the mark on the balancer. When the engine is running the timing light will strobe and illuminate the balancer mark as it spins. To adjust the timing loosen the distributor and turn slightly one way or the other to achieve the desired setting. Once an adjustment has been made re-tighten the distributor hold down bolt or bolts.

Exhaust systems have an air injection system designed to help the complete consumption of exhaust gasses. This added air is only in operation during power mode. If the air injection check valve or sometime referred to as a "gulp valve" fails it can allow extra air into the exhaust system causing system internal and external backfiring. To check your systems valve remove it and blow in ti both ways to check air flow. Air should only travel one direction hence the name: "check valve". If air travels both directions the valve has failed and needs replacement, this is a common problem.
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Sunday, March 1st, 2009 AT 8:48 PM
Tiny
GARYLEE STIFFLER
  • MEMBER
Was driving my truck and it just died. I putt a new new fuel pump, plugs, distributor, crank sensor, timing chain, new cap and rotor still backfires through exhaust. Once further checking from a professional It was the ecm. We replaced it and it fixed the problem.
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Friday, April 29th, 2016 AT 11:14 AM
Tiny
KEN
  • ADMIN
Good to hear, please use 2Carpros anytime

Best, Ken
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Tuesday, August 16th, 2016 AT 11:48 AM

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