96 buick roadmaster just replaced plugs and air filter still has a backfire
If it's a backfire like a gunshot when you turn off the engine it's the diverter valve for the A.I.R. system. Replace it. HTH. -Jim
You might need to check the wires to see if they are not cross firing. Since they run so close to the exhaust manifold might be a good idea. My daughters 96 rodie wagon had two wires firing into each other because they where burnt/dried out from age.
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