Is it back pressure?

[1929]

When slowing down from a higher speed to stop at the light, there is sometimes a sputtering noise out the muffler, is that back pressure?

[tbirdtbird]

Back pressure from an exhaust system is there all the time.
When 'backing down' as you describe with the throttle plate fully closed the mixture is very lean and you can get that sound. If it bothers you try opening the GAV 1/4 turn more, but I would not bother. Possibly even adjust the idle mixture screw to richen it up a bit

[J Franklin]

Rich in the mixture
Poor in the pocketbook

[1929]

Originally Posted by tbirdtbird

Back pressure from an exhaust system is there all the time.
When 'backing down' as you describe with the throttle plate fully closed the mixture is very lean and you can get that sound. If it bothers you try opening the GAV 1/4 turn more, but I would not bother. Possibly even adjust the idle mixture screw to richen it up a bit

I have the opening at a 1/4 rom fully closed, I also have the idle very low.

[100IH]

Exhaust leaks at the exhaust manifold, especially where the exhaust and the muffler assy. meet can cause this because fresh air can be drawn in to let the un-burned hydrocarbons to re-ignite. Also, too lean of a mixture can cause a lean misfire and pass along un burned vapors for ignition after the exhaust stroke similar to the over rich scenario.

[C26Pinelake]

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Originally Posted by tbirdtbird

Back pressure from an exhaust system is there all the time.
When 'backing down' as you describe with the throttle plate fully closed the mixture is very lean and you can get that sound. If it bothers you try opening the GAV 1/4 turn more, but I would not bother. Possibly even adjust the idle mixture screw to richen it up a bit

Great advice. I think many A's do it ! Wayne

[SeaSlugs]

gonna say pretty normal for this to happen with any vehicle with a leaky exhuast system under engine braking. or if you have glasspacks installed... or no muffler because it rotted off AGAIN... ( amazing how an s10 can sound like a tractor when you bog the engine at low speed)