Backfires/ popping

1988 GMC SUBURBAN
260,000 MILES • 5.7L • V8 • 2WD • AUTOMATIC
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BOYDEN
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When I accelerate there is a popping sound coming from the Muffler? It only does it when I accelerate? What can cause this?
Aug 17, 2016 at 8:27 PM
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HMAC300
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check for a bad valve meaning engine compression all cylinders and look for a bent pushrod or broken rocker arm after you short out cylinders by removing plug wire to find which one it is.
Aug 18, 2016 at 6:28 AM