› Forums › Car Problems & Maintenance › Mercury › Why does my 1963 Mercury 390 backfire only at idle?
May 13, 2025 at 7:28 pm
#1390
Ed Degelsmith
Make sure the jets on the carb are clean. I had a motorcycle that did the same thing and when I had the carburetor off I decided to clean it. Then the backfire popping sound disappeared.