Slight backfire at shift
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Intermediate
Joined: Feb 2021
Posts: 32
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From: Parish, NY
Slight backfire at shift
Not that I do it very often, but taking of in rapid exceleration I got a very slight backfire at shift from 1st to 2nd and again from 2nd to 3rd. It was minor but noticeable. Thought on the cause and remedy? Never done it before and the car has 7500 miles (2017 GS)
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From: Cape Coral, Florida
Moderator, Tech Contributor
Joined: Sep 2013
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From: Cape Coral, Florida
Does it sound like it’s coming from the intake or exhaust ??...best thing is to put a scan tool on the car to see what DTC’s you may have and the first data PID I would look at are your fuel trims just to get some direction.
Last edited by C5 Diag; May 1, 2021 at 07:49 PM.
Burning Brakes
Joined: Nov 2016
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From: San Dimas CA
Burning Brakes
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From: San Dimas CA
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From: Cape Coral, Florida
Burning Brakes
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From: San Dimas CA
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Verdad Gallardo
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Joined: Sep 2013
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From: Cape Coral, Florida
Never heard of an acell POP !!...it’s decell fuel cut off...you’re telling me this is an acell fuel cut as you call it then ??...post this article !!...do what’s causing this “pop “ then ??
Last edited by C5 Diag; May 1, 2021 at 08:29 PM.
Le Mans Master
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From: Atlanta GA
Le Mans Master
Joined: Oct 2014
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From: Atlanta GA
Dave
Le Mans Master
Joined: Oct 2014
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From: Atlanta GA
Why would there be a TSB OR SI for something that is perfectly normal on a A8 , for a split millisecond fuel and spark is cut during a WOT upshift on the 1st to 2nd and then again on the 2nd to 3rd upshift . Corvettes are not the only cars that do this
Dave
Dave
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From: Cape Coral, Florida
Thanks !!...I’ll look into this !!
Le Mans Master
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Pro
Joined: Mar 2006
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From: EAST TEXAS
One clarification. To cut/unload the torque on the transmission clutches and gears during hard acceleration, the ignition is cut during the shift for a very brief time. The fuel is not cut, so for a few engine revolutions, fuel is being sent thru the injectors, in and out of the cylinders, and out the exhaust, without being burned. Then, when the ignition is switched back on, the unburned fuel in the the exhaust system is ignited by the fresh hot exhaust and produces an obvious pop or bang. Very normal.